This article is from the archive of our partner National Journal

Candidates matter, campaigns matter, spending matters, and local quirks matter, too. But, like all elections, this fall's midterm has also been heavily shaped by systemic structural factors that transcend the competitions between individual candidates.

As the campaign careens toward its close, keeping some of these factors in mind may help keep in perspective what Tuesday's results will—and won't—say about the balance of power between the parties. What are those structural factors? Four seem to me the most important:

1. The president's party almost always performs poorly in midterm elections, particularly the midterm of a second presidential term. Since 1900, the president's party has lost both House and Senate seats in 19 of the 28 midterm elections; in the other nine cases, the president's party gained seats in both chambers three times, and gained seats in one chamber—but not the other—six times. The numbers have been especially consistent in sixth-year elections: Although Republicans performed well in the midterms after the reelections of William McKinley in 1900 and Theodore Roosevelt in 1904, the president's party has lost a significant number of seats in every other six-year-itch election since then, except for 1998, when Democrats benefited from the backlash against the House Republican drive to impeach Bill Clinton. In those other nine cases—1918, 1926, 1938, 1946, 1958, 1966, 1974, 1986, and 2006—the president's party averaged a loss of 7.2 Senate seats and 37.4 House seats. Those may be good yardsticks to keep in view on Tuesday night.

2. The modern Democratic coalition is a boom-and-bust coalition that depends heavily on minorities and young people who turn out much less regularly in midterm than presidential elections. Older voters, who are trending steadily toward the GOP, vote much more reliably. Beyond any short-term factors, this is creating a structural disadvantage for Democrats in off-year elections: an electorate that is consistently older and whiter than it is in presidential races. As I wrote recently in The Atlantic: "In the five presidential elections from 1992 through 2008, exit polls conducted for a consortium of media outlets found that voters under 30 cast, on average, 18 percent of the ballots; in the five midterms that immediately followed those elections, young people accounted for just 12 percent of the votes. Voters over 65, by contrast, increased their share of the vote from 15 percent to 19 percent. The decline among minorities hasn't been as consistent or as severe, but their share of the vote dropped two percentage points from 2004 to 2006, and three from 2008 to 2010, which are big shifts as these things go."

Ironically, because Democrats have succeeded in turning out more minorities in presidential years, census figures show that the falloff in participation among Hispanics and African-Americans from an on-year to an off-year election is about twice as large as it was three decades ago. The most recent experience offered Democrats a daunting precedent: From 2008 through 2010, turnout dropped about one-third for African-Americans, almost two-fifths for Hispanics, and fully 55 percent for 18-to-24-year-olds, compared with about one-fourth for whites and only one-eighth for seniors. Tuesday's election will help tell us how much the Democrats' unprecedented efforts to identify and mobilize their core supporters can offset these underlying midterm trends, particularly in the battleground states both sides are targeting.

3. As more Americans pick Senate candidates from the same party that they usually support for president, each party is struggling to hold Senate seats in effect behind enemy lines—in states that usually prefer the other side for the White House. That trend is affecting both parties, but this year, it benefited Republicans. The core of the Democrats' vulnerability this year has been a map tilted heavily toward places evolving away from the party, partly because the voters who comprise their new coalition are less prevalent there. Heading into this election, Democrats held 43 of the 52 seats in the 26 states that twice supported President Obama, and Republicans controlled 34 of the 44 in the 22 states that twice opposed him. This year, Democrats were especially vulnerable because they needed to defend six of their 10 red-state seats, and a seventh in North Carolina, which supported Obama in 2008 but not in 2012.

One reason those states are growing away from Democrats harkens back to my second point: Their electorates are heavily influenced by the blue-collar, older, and rural white voters who have trended away from the party since the 1970s—but with increasing speed under Obama. In each of those seven states except Louisiana and North Carolina, the nonwhite share of the vote in 2008 was lower than the national average. As I wrote earlier this year, "In 2008, when Democrats won their Senate seats in those seven states, whites without a college degree cast at least half the votes in four of them (Arkansas, Montana, South Dakota, and West Virginia) and about two-fifths in Alaska and Louisiana. Whites older than 45 represented about half or more of the electorate in those first four states, and around two-fifths in Alaska and North Carolina." Outgoing President George W. Bush's unpopularity offset those unfavorable demographics in 2008. This year, Obama's unpopularity is compounding their impact. Which brings us to the final headwind facing Democrats: 

4. Americans are disillusioned with Obama. With a Gallup approval rating around 42 percent through the average of his 23rd quarter in office, Obama stands well below where Dwight Eisenhower (56 percent in 1958), Ronald Reagan (62 percent in 1986), and Bill Clinton (64 percent in 1998) did at this point in their presidencies, and closer to George W. Bush (39 percent). Two presidents who presided over a second-term midterm election after taking over a presidency already in progress also stood at least slightly ahead of Obama: Lyndon Johnson checked in at 44 percent in fall 1966 (six years after John F. Kennedy's election) and Gerald Ford reached around 50 percent in 1974 (six years after Richard Nixon's).

It's worth noting that despite the wide variation in those approval ratings, the president's party lost seats in each of those sixth-year elections except Clinton's. All of that suggests Democrats likely would have faced very tough elections in red states even if Obama's approval rating was better. But his decline made the incline tougher for red-state Democrats, and unquestionably has helped Republicans expand the Senate map into places like Colorado, Iowa, and New Hampshire, each of which voted for him twice. Although there are always candidates who can escape the president's gravitational pull, they are growing more rare. In 2006, Republican Senate candidates lost 19 of the 20 races in the states where exit polls showed Bush's approval at 45 percent or below; in 2010, Democrats lost 13 of the 15 races in states where polls showed Obama's standing at 47 or below.

In addition to these four key structural factors, there is another crucial point to remember: This year's results don't necessarily predict the 2016 outcome. Since the turn of the 20th century, when the president's party has performed poorly in the midterm, it has lost the next presidential election about half the time—and won it the other half. (When the president's party has defied the trend and avoided midterm losses in even one chamber since 1900, it has won all but one of the succeeding presidential races—2000, when Democrats won the popular vote but narrowly lost the Electoral College.)

A Republican Senate takeover would ensure the White House plenty of headaches over the next two years. But the longer-term trend in the Senate is toward more fragile and fleeting majorities: If Republicans take the Senate this week, neither side will have held it for more than eight consecutive years since 1980, a period of volatility unlike anything since the late 19th century. Unless the bottom falls out for Democrats—and Republicans make big enough gains to establish a meaningful cushion—even a newly elected GOP majority would instantly face the risk of handing back the Senate gavel in 2016 because it must defend seven seats that year in states that twice voted for Obama.

With the longer-term Senate trend pointing toward more frequent flips in control, the larger question may be what Tuesday will say about the Democrats' ability to hold the White House in 2016. Given the varying turnout patterns of some of its core supporters (including young people, minorities, and single white women), as well as their geographic concentration in major urban areas, the modern Democratic coalition is arguably better suited to control the presidency than the Congress.

Obama has reinforced that disparity by leading the party to more consistently embrace the mostly liberal priorities of its new national coalition, particularly on noneconomic issues like immigration, gun control, gay rights, abortion, contraception, and climate change; every Senate Democrat, for instance, voted to provide a pathway to citizenship for undocumented immigrants and to guarantee equal treatment for gays in the workplace, and all but four supported universal background checks for gun sales.

All of these issues align the Democrats with the preferences of the coalition that has allowed them to win the popular vote in five of the past six presidential races—but further alienate the older and blue-collar white voters that red state Congressional Democrats must attract to survive. In the long run, it's unlikely that a party that consistently takes culturally liberal positions on all of these issues will hold most House and Senate seats in the culturally traditionalist interior states across the South and Plains, where those views face the most resistance. Over the long term, Democratic congressional majorities will likely depend on the party winning more House and Senate seats in racially diverse states (and districts) in such places as Georgia, Texas, Arizona, and Florida.

But in 2012, Obama emphatically demonstrated that Democrats could win the White House now without much support from either culturally conservative voters or states. With solid support from the groups in the party's new coalition, Obama won a relatively comfortable reelection despite losing over three-fifths of both whites without a college degree and whites over 45—and despite watching Mitt Romney capture a higher overall share of the white vote than Reagan in 1980.

In 2016, it's likely that Democrats can withstand an even weaker performance among whites. If demographic change follows its recent trajectory, the minority share of the vote in 2016 will likely rise to 30 percent—up 2 percentage points from 2012. Except for John Kerry in 2004, every Democratic presidential nominee since 1976 has won between 78 and 82 percent of the two-party vote among nonwhite voters.

That means if the minority vote follows its durable trends in both share and performance, the 2016 Republican nominee will need to win almost 63 percent of whites to assemble a national majority. That's roughly equal to the 64 percent of whites that Reagan carried in 1984—en route to the most resounding landslide of modern times. Structural changes since Reagan's day inside the white electorate—shifts from the reliably red blue-collar, married, and religious toward white-collar, single, and secular voters more open to Democrats—make that hill even steeper.

That's not to say Republicans could not climb that peak in 2016, but only to underscore that it's a more difficult ascent than consolidating red states and even picking off a few blue-leaning places in a midterm election. Indeed, if the 2016 Republican nominee wins the same share of whites that polls show the party positioned to capture in the 2014 House races, the Democrat would win the next presidential race—absent meaningful GOP gains with minority voters.

Republicans don't need to look very far back to grasp that truth. In 2010, the exit polls found that Republican House candidates won 60 percent of white voters (for the first time in the history of polling) and the GOP enjoyed the biggest midterm House gain for either party since 1938. Two years later, Romney virtually matched them by taking 59 percent among white voters and didn't come close to retaking the White House. Recognizing that reality, two prominent GOP strategists—Neil Newhouse (Romney's lead pollster) and Glen Bolger—issued a firm warning last week in a Washington Post op-ed: "Winning in a non-presidential-turnout year, when older and white voters make up a larger percentage of the electorate, should convince no one that we've fixed our basic shortfalls with key electoral groups, including minorities and younger voters." Karl Rove, the chief strategist for George W. Bush's two victories, has raised similar red flags.

Geography sends similar caution signs to the GOP. For all of their likely gains this year, Republicans almost certainly won't dislodge any Democratic Senate seats from what I've termed the Blue Wall: the 18 states Democrats have carried in at least the past six consecutive presidential elections. Even in 2010, when a cresting wave helped Republicans take Blue Wall Senate seats in Illinois, Pennsylvania, and Wisconsin, the party could not follow up by capturing those states in the next presidential race. Although Republicans this year have reaffirmed their ability to compete for states at the edge of the modern Democratic map—Colorado, Iowa, New Hampshire—until they show they can break the Democrats' hold on some of the core Blue Wall's 242 Electoral College votes, the GOP will begin the presidential race in a geographic hole. As Newhouse and Bolger wrote, "Republicans were not able to put any Senate races in those Blue Wall states in play. Thus the GOP 'strategy' [for 2016] is essentially to be perfect in purple states—not a game plan with a high probability of success."

Still, the warning signs for Democrats this year are clear. Polls consistently show that most Americans now question Obama's management of both the economy and the nation's security—doubts that have weighed on Democratic candidates in all competitive races. Throughout American history there are very few examples of the president's party holding the White House for a third term when a president who won reelection and is retiring faces as much discontent as Obama does now. That was true in 1920 (when Woodrow Wilson left office); 1952 (with Harry Truman); 1968 (with Johnson) and 2008 (with Bush). (The clearest exception may be 1876, when Rutherford B. Hayes narrowly succeeded scandal-tarred Ulysses Grant in what was the closest and most bitterly disputed election until 2000.)

More immediately, the huge deficits most Democratic candidates face among almost all but the most culturally liberal segments of the white electorate (particularly single and college-educated white women) underscores Obama's inability to build support for his party's vision of activist government. Democrats move into the final stages of his presidency facing overwhelming skepticism in the white middle class that initiatives from Washington can improve their lives. That problem long predates Obama, of course, but he has failed to solve it and in some ways has magnified it: Surveys have consistently found that most whites do not believe they benefited from either his 2009 economic stimulus or the Affordable Care Act. Even millennial generation whites, though drawn to Democrats on social issues, share that skepticism, polls show—an opening that could allow for more Republican inroads with them on Tuesday.

Continued economic recovery may somewhat improve those sentiments. Though stagnant incomes discouraged Democratic candidates this year from trumpeting these numbers, the economy has already created more than five times as many net new jobs under Obama as it did during George W. Bush's entire presidency—and that gap is certain to widen further by 2016. Affinity on cultural issues, which usually looms larger in a presidential race, may also give Democrats a more powerful lever in 2016 to sustain support from socially liberal whites unconvinced about activist government. And far from confronting their challenges with the growing populations of minority and socially liberal white women, Republicans show all signs of compounding them, for instance with hard-line positions on immigration. But if Tuesday marks a third consecutive election when Democrats lose about three-fifths of whites, it will harden a Republican advantage that keeps the presidential race in doubt, despite the steady growth of voting blocks that lean toward Democrats, particularly on culture.

In simplest terms, the basic story of the modern standoff between the parties is that Democrats cannot attract enough whites to consistently control Congress, and Republicans cannot attract enough nonwhites to consistently win the White House. Nothing that happens this week is likely to displace that truth. If Tuesday's results produce the GOP gains that now appear most likely, the stage will be set for a titanic 2016 presidential election between a Democratic Party weakened by deepening disenchantment with Obama's performance, and a Republican Party hobbled by its difficulty adapting to changing demography.

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

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