This article is from the archive of our partner National Journal

Less than a month before Election Day, dozens of House races are still in flux—but Democratic incumbents face far more coin tosses than Republicans, meaning the GOP is likely to expand its majority in the House of Representatives this November. Republicans expect moderate gains this cycle, using a favorable political climate to attack a slew of Democratic freshmen and add to their already solid majority. But few of those districts are obvious wins: Democratic incumbents like Carol Shea-Porter of New Hampshire, Ann Kirkpatrick of Arizona, and Bill Enyart of Illinois—among the most endangered Democrats on the ballot—still have roughly 50-50 shots at being reelected, according to a survey of strategists from both sides who are watching and working on these races.

Republicans have a large number of pickup opportunities to choose from this year. Fifteen of our 30 top races are districts where Republican challengers have legitimate shots at beating Democratic incumbents. That's in addition to two safe bets for the GOP and nine other open-seat races.

Democrats, meanwhile, are on offense in a select number of districts, hoping to pick off several seats where Republican incumbents have tripped over their own feet. In New York, Rep. Michael Grimm's fraud indictments dealt his reelection prospects a heavy blow. In Florida, Rep. Steve Southerland's gender-centric gaffes may have alienated women voters, making Gwen Graham an even stronger challenger—and Republicans already knew the political scion was a threat. And in Nebraska, Rep. Lee Terry's refusal to give up his own pay during last year's government shutdown continues to be an anchor on his reelection hopes.

For Republicans, the races that have fallen off the radar are just as important as some of their pickup opportunities. Incumbents like Rodney Davis, Dan Benishek, Mike Fitzpatrick, Joe Heck, and David Valadao look significantly more safe than they did at the start of the election cycle or even a few months ago. That has allowed Republicans to go on the offensive, spending very little money on retaining seats.

While the Senate and gubernatorial races are awash in polling data right now, detailed, nonpartisan polls are hard to find in House races. These ratings are based partly on what polls are out there, but also on National Journal's cumulative research and reporting on these districts, including financial information, historical data, and information from the campaigns, party committees, outside groups, and activists involved in these races.

These rankings focus on which districts are most likely to flip from one party to another, with the most likely suspects listed at the top. That includes several races that are no longer considered competitive, like Mia Love's campaign in Utah. It does not include competitive intra-party races like Rep. Mike Honda's reelection campaign in California. With that, here is our list of the 30 House districts most likely to change hands this fall.

1. UT-04: Democratic Rep. Jim Matheson retiring. Republican Mia Love, former mayor of Saratoga Springs, is the heavy favorite to win in one of the most heavily Republican-leaning districts currently held by a Democrat. Mitt Romney won 67 percent of the vote in this district in 2012 while Matheson just squeaked by against Love; without the incumbent Democrat on the ticket, this is Love's seat.

2. NC-07: Democratic Rep. Mike McIntyre retiring. Republican David Rouzer has a major advantage in another conservative district. Democrat Jonathan Barfield isn't seen as a serious contender in a district Romney won by a 20-point margin in 2012.

3. CA-31: Republican Rep. Gary Miller retiring. Democrats should have beaten Miller two years ago, but a mass of Democrats in the district's top-two primary led to a two-Republican general election after the progressive vote split in the primary. Democrats faced a similar scenario this cycle, but Redlands Mayor Pete Aguilar survived the primary and is favored to beat Navy veteran Paul Chabot.

4. NY-21: Democratic Rep. Bill Owens retiring. Democrats have clearly lost confidence in their prospective replacement for Owens. The Democratic Congressional Campaign Committee pulled two weeks of airtime supporting documentary filmmaker Aaron Woolf. It doesn't help that Green Party candidate Matt Funiciello could pull a significant number of votes from Woolf. Recent surveys have shown Republican Elise Stefanik leading Woolf and Funiciello picking up a healthy level of support for a third-party candidate.

5. IA-03: Republican Rep. Tom Latham retiring. It hasn't been a perfect campaign for Democratic former state Sen. Staci Appel—her missteps on national security in a debate gave Republicans an easy target in attack ads—but she still holds an edge over her Republican opponent, former congressional aide David Young. Appel holds a major financial advantage over Young, who struggled to win the Republican nomination while Appel faced no primary competition. A Democratic poll showed Appel with a 3-point lead in late September, and a Loras College poll earlier in September showed her with a 6-point lead.

6. NH-01: Democratic Rep. Carol Shea-Porter running for reelection. Shea-Porter looks like the most vulnerable incumbent in the country because of a hostile political atmosphere and a strong challenger. Public polling between her and ex-Rep. Frank Guinta, the Republican nominee, has been all over the map. Guinta beat Shea-Porter soundly in 2010 and lost to her by a narrow margin in 2012. With lower turnout this year and a tougher atmosphere for Democrats, Guinta seems to have an edge in this quintessential swing district.

7. AZ-01: Democratic Rep. Ann Kirkpatrick running for reelection. Kirkpatrick faces an even harsher political atmosphere in a district where Republicans are confident that voters' concerns over Obamacare and immigration will drag down any Democrat. But she has a slight advantage in that her opponent, Republican state House Speaker Andy Tobin, struggled through his primary and has to earn the support of tea partiers who previously opposed him. Republicans have released two polls showing Tobin leading. Democrats have pointed to the polls' unusually low samples of Native Americans, who overwhelmingly support Kirkpatrick, but they haven't released any polls of their own. Kirkpatrick has shown enough independence and authenticity to earn The Arizona Republic's endorsement, but this is still one of the top districts where President Obama's unpopularity is an anchor for any Democrat. After all, Obama didn't carry it in either 2008 or 2012.

8. NY-11: Republican Rep. Michael Grimm running for reelection. The line of attack against Grimm is clear: He was indicted on 20 counts relating to skimping on payroll taxes while employing undocumented immigrants at his restaurant. And he threatened to throw a reporter off a balcony and break him in half, "like a boy." Some of that negative press may not resonate with some loyal supporters, but it's hard to see this race going anywhere but downhill for Grimm. A mid-September Democratic poll shows Grimm tied with former New York City Councilman Domenic Recchia, and an earlier Siena College poll showed Grimm with a 4-point lead.

9. IL-12: Democratic Rep. Bill Enyart running for reelection. Like Kirkpatrick, Enyart isn't particularly well-known, which may be what forced the DCCC, which usually runs attack ads, to air positive TV spots boosting Enyart this fall. Enyart faces a challenge from high-profile Republican state Rep. Mike Bost in a moderate-to-conservative downstate district where Gov. Pat Quinn's coattails, or lack thereof, aren't much help. A mid-September survey by the Republican-affiliated Tarrance Group showed Bost with a 4-point lead, but as with most House races, detailed data is tough to come by.

10. FL-02: Republican Rep. Steve Southerland running for reelection. Southerland has dug himself into a hole with women voters, first holding a men-only fundraiser that directed attendees to "tell the Misses not to wait up," and then responding to accusations of sexism by saying he lives with five women and asking if his opponent had "ever been to a lingerie shower." More importantly, Southerland faces attorney Gwen Graham, the daughter of popular former Democratic Sen. and Gov. Bob Graham. Graham may be Democrats' top triple threat: She's a prolific fundraiser, she has high name identification, and she has no political record that can be used against her—though that hasn't stopped Republicans from trying to tie her to Minority Leader Nancy Pelosi.

11. NE-02: Republican Rep. Lee Terry running for reelection. Last year's government shutdown hasn't hurt any incumbent as much as it's hurt Terry, who refused to give up his pay during the shutdown because, he said, he had "a nice house and a kid in college." This wasn't seen as a top-tier race earlier this cycle, but Democratic state Sen. Brad Ashford has kept the focus on congressional pay and perks, calling for a 10 percent congressional pay cut—which Terry unwisely sided against.

12. WV-03: Democratic Rep. Nick Rahall running for reelection. Rahall is swimming against a strong political current. Romney won his district with 65 percent of the vote in 2012, and the Environmental Protection Agency's proposal to limit carbon emissions has led this race to focus heavily on Obama's "war on coal." But he has held this seat since 1977 and is familiar to voters. He's also successfully pushed back against ads by Americans for Prosperity, tying his opponent, state Sen. Evan Jenkins, to "out-of-state billionaires from New York City." Still, his levels of support have fallen in recent elections, and Republicans remain optimistic they can tip him below a winning margin this year.

13. GA-12: Democratic Rep. John Barrow running for reelection. Barrow is in the same boat as Rahall. They both represent districts that heavily favor Republicans, but also have strong reputations individually, and Barrow is a particularly good campaigner and performer in TV ads like this one. Like Rahall, Barrow touts his endorsement from the National Rifle Association. Construction-company owner Rick Allen could beat Barrow, but the burden is on him to unseat a well-known incumbent.

14. IL-10: Democratic Rep. Brad Schneider running for reelection. Schneider isn't in as bad shape as fellow Illinois Democrat Enyart, but he faces a challenge from former Rep. Bob Dold, and has been targeted by the U.S. Chamber of Commerce and Crossroads GPS. Schneider was one of four incumbents whom the DCCC bought more airtime to support this week.

15. AZ-02: Democratic Rep. Ron Barber running for reelection. Barber faces one of the top Republican challengers in the country: retired Air Force fighter pilot Martha McSally, whom he beat by only about 2,500 votes in 2012. But Barber, who replaced Gabrielle Giffords in the House two years ago, has also played his cards right, touting his independence from party politics and support for tougher border security. Public polling has been scarce; a June poll conducted for Democrats' House Majority PAC showed Barber with an 8-point lead. The race is still widely viewed as a toss-up.

16. FL-26: Democratic Rep. Joe Garcia running for reelection. Garcia also faces a prized Republican recruit in Miami-Dade County School Board member Carlos Curbelo. The National Republican Congressional Committee has run repeated ads on Garcia's ethics issues—his former campaign manager pleaded guilty to absentee-ballot fraud. But Curbelo has suffered from some bad press, too: He was recently captured on camera calling Social Security a "Ponzi scheme" while talking to a group of College Republicans. An early September internal poll for Curbelo showed him with a 4-point lead. The next couple weeks will show us whether Curbelo's poll was on the money or optimistic—and whether his comments have affected the race.

17. CA-52: Democratic Rep. Scott Peters running for reelection. Peters and former San Diego City Councilman Carl DeMaio appear deadlocked. Polling in the district, much of it from the automated firm SurveyUSA, has bounced around. And the DCCC and NRCC have spent roughly the same amount on the race so far. Both candidates hope to negatively define each other, with Peters tying DeMaio to the tea party and DeMaio blaming Peters for San Diego's pension crisis.

18. CO-06: Republican Rep. Mike Coffman running for reelection. Coffman represents a nearly 20 percent Latino district that Obama won by a 5-point margin in 2012, and his opponent, former state House Speaker Andrew Romanoff, has proved to be a strong fundraiser. But Coffman has benefitted from more outside spending, and hasn't made any major mistakes on the campaign trail like Southerland or Terry (or the 2012 vintage of Coffman, for that matter).

19. CA-07: Democratic Rep. Ami Bera running for reelection. Bera appears to have about a 50-50 chance at reelection over Republican former Rep. Doug Ose. Last month, a Democratic poll showed Bera with a 4-point lead, and a Republican poll showed Ose with a 4-point lead. The district leans slightly Democratic, but both polls showed Obama's approval rating underwater.

20. AR-02: Republican Rep. Tim Griffin retiring. Democrats hope this could be their biggest surprise pickup. The district is conservative, but Democrat Patrick Henry Hays, the former mayor of North Little Rock, has been on the airwaves to tout his work attracting local jobs and balancing the town's budget. And the DCCC has aggressively gone after "millionaire banker" French Hill. An internal poll showed Hays holding a 3-point edge over Hill, perhaps explaining why the DCCC recently reinforced its ad buy here.

21. VA-10: Republican Rep. Frank Wolf retiring. Republican state Del. Barbara Comstock, who used to work for Wolf, hopes to run on his legacy—Wolf even appeared in her first TV ad. But the increasingly diverse (and increasingly blue) district is in play for Fairfax County Supervisor John Foust. Perhaps the biggest barrier to Democrats flipping this seat: Foust accused Comstock, who has mostly worked in politics, of never having "a real job," which Republicans called sexist. If Foust fails to hold an advantage among women voters, this could be a wasted opportunity for Democrats.

22. MN-08: Democratic Rep. Rick Nolan running for reelection. Stewart Mills, "the Brad Pitt of the Republican Party," turned Nolan's reelection bid into a toss-up despite Democrats' slight registration advantage in the district. Nolan also seemed to run a lethargic campaign—although his recent announcement that he raised an impressive $641,000 in the third quarter of the year looks like a good sign.

23. MA-06: Democratic Rep. John Tierney lost primary. Democrats have a better chance at holding this seat now that Marine Corps veteran Seth Moulton is their candidate instead of Tierney, whose family's racketeering convictions would have been a burden. Republican former state Sen. Richard Tisei nearly beat Tierney in 2012. He's still a contender this cycle, but he has less to run against, though Moulton has to replenish his campaign cash quickly after the September primary.

24. WV-02: Republican Rep. Shelley Moore Capito running for Senate. The open-seat race may be Democrats' most ambitious legitimate attempt at flipping a seat. Like West Virginia's 3rd District, this is a conservative area where Obama is unpopular. But Democrats hope that Republican Alex Mooney, who lived in Maryland and considered a congressional run there before moving across the border, fails to connect with voters who see him as a carpetbagger. Nick Casey, the former chairman of the West Virginia Democratic Party, has struck a bipartisan tone in the hopes of winning over independents and Republicans who want a local to represent them.

25. NY-01: Democratic Rep. Tim Bishop running for reelection. Bishop faces a tough reelection bid partly because of allegations that he asked for a campaign contribution after helping a constituent get a permit. The NRCC has run TV ads calling Bishop "corrupt and proud of it." But a Siena College poll last month had Bishop leading Republican state Sen. Lee Zeldin by 10 points.

26. ME-02: Democratic Rep. Mike Michaud running for governor. This district leans left, but Michaud's gubernatorial run has left the seat open and given Republicans hope at an upset. Republican former state treasurer Bruce Poliquin led a small University of New Hampshire poll by 10 points, but he is still seen as an underdog to Democratic state Sen. Emily Cain, who has a collection of major Democratic groups backing her up.

27. CA-26: Democratic Rep. Julia Brownley running for reelection. Brownley's district also favors Democrats, but Democrats have acknowledged that state Assemblyman Jeff Gorell is keeping the race close, and the Congressional Leadership Fund is spending $500,000 to support Gorell. This Ventura County-based district is changing quickly, and Republicans may not get another good shot at it for a while if Gorell can't beat Brownley this year.

28. NJ-03: Republican Rep. Jon Runyan retiring. After Runyan announced his retirement, this moderate district was a top target for Democrats. But when wealthy, center-right Republican Tom MacArthur won the nomination over Steve Lonegan, the race turned slightly in Republicans' favor. Democrat Aimee Belgard, a Burlington County Freeholder, still could win—a September poll showed her and MacArthur exactly tied at 42 percent each—but the self-funding MacArthur has a significant financial advantage.

29. NY-24: Democratic Rep. Dan Maffei running for reelection. Maffei, who lost his seat in 2010, isn't safe, but he has an edge over attorney John Katko. Maffei led a Siena College poll by 8 points last month, and he had a more than $1 million cash advantage over Katko as of July. Still, Maffei's .500 record in past House races isn't settling Democratic nerves.

30. MN-07: Democratic Rep. Collin Peterson running for reelection. Peterson has represented his conservative-trending district since 1991, but Republicans are high on state Sen. Torrey Westrom, who has a compelling personal story. Both Democrats and Republicans have released polls showing Peterson with a lead, but the NRCC has spent nearly $3 million on airtime in the district to try and change that, while Democrats insist Peterson's personal brand can withstand anything they throw at him.

Honorable mentions: In TX-23, Democratic Rep. Pete Gallego is relatively popular but faces a challenge from former CIA agent Will Hurd in an evenly split district. In NY-18, Democratic Rep. Sean Patrick Maloney faces a challenge from former Rep. Nan Hayworth. In CT-05, Democratic Rep. Elizabeth Esty faces a challenge from businessman Mark Greenberg. In CA-21, Republican Rep. David Valadao faces Amanda Renteria, the first Latina chief of staff in Senate history, in a majority-Latino district. In AR-04, Democrats hope James Lee Witt, who served as FEMA director under President Clinton, can overcome the district's conservative leanings in an open-seat race. In MI-01, Republican Rep. Dan Benishek faces a challenge from Army veteran Jerry Cannon. In IL-13, Republican Rep. Rodney Davis seems to have pulled away from highly touted Democratic challenger Ann Callis, a former county judge. In NY-23, Democratic Tompkins County Legislator Martha Robertson is challenging Republican Rep. Tom Reed. In HI-01, Democratic state Rep. Mark Takai is considered the favorite over Republican Charles Djou, who briefly served in Congress after winning a special election in 2010.

This article is from the archive of our partner National Journal.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.