Alan Grayson: The face of the Democrats' antiestablishment wing.Mark Wilson AFP/Getty

If Hollywood wanted to produce a superhero movie about an eclectic bunch of Democratic Senate underdogs looking to take on their party’s establishment, they wouldn’t be able to script a more unusual cast of characters than the ones actually running: There’s a three-star admiral who has no interest in taking orders from party leaders. There’s the wealthy left-wing millionaire whose main campaign “talent” is to pulverize his opposition, at least rhetorically. There’s a boyish 30-year-old Cincinnati city councilman who’s looking to play David to a former Ohio governor’s Goliath. And there are two highly accomplished African-American women vying to make history in the Senate—but both trying to do it against candidates who enjoy the backing of the Democratic establishment.

None of these candidates are favorites to win their party’s primaries, running against better-funded, better-organized Democratic opposition. But the mere fact that they’re not being cowed by party leaders to step aside for the greater good is a reflection of the rising tide of progressive, antiestablishment angst taking place within the Democratic Party. Just as the once-seemingly unbeatable Hillary Clinton is looking more vulnerable than ever in the presidential campaign, some of the party’s brand-name Senate front-runners can’t depend on big-name endorsements translating into public support.

The spate of credible Democratic primary challengers creating headaches is unusual for the party, at least in recent history. Over the past decade, only one election year (2010) featured a string of competitive Democratic Senate primaries in battleground states. More often than not, the party’s congressional leaders have been successful in anointing favored candidates without much interference from the outside. When Democrats have faced competitive Senate primaries, they’ve usually been in liberal states where the general election is a fait accompli. By contrast, four of next year's five biggest primaries are in battleground races where a divisive fight for the nomination could hurt the eventual Democratic nominee.

With the compelling presidential race sucking up all the media oxygen lately, the battle for the Senate hasn’t gotten much attention. But these primaries are worth following to get a measure for how deep the Democratic Party’s divisions are. In a normal year, the front-runners would be expected to coast. In another year, the notion of a 30-year-old political novice taking on a brand-name politician would be seen as a joke. Before the rise of Donald Trump as a politician, few would entertain the notion of a boorish multi-millionaire beating the party’s endorsed candidate in Florida.  But this is not shaping up to be a normal political environment.

The most interesting test will be in Pennsylvania, a race critical to Democratic hopes of retaking the Senate. Party leaders got so tired of the unpredictability of former Rep. Joe Sestak, the highest-ranked military officer to ever serve in Congress, that they recruited Katie McGinty, the fourth-place finisher in last year’s gubernatorial primary. On paper, Sestak is an accomplished candidate as a decorated military veteran, former Philadelphia-area congressman, and someone who nearly bucked the 2010 Republican wave in the Keystone State. He fits the political moment as a political outsider willing to buck the party establishment—so much so that he wouldn’t even tell the Democratic Senatorial Campaign Committee about his campaign launch.

But wary of his unconventional campaign approach, party leaders felt it was worth the risk to recruit McGinty, a more conventional politician (most recently, she served as Gov. Tom Wolf’s chief of staff) even though it’s sparking a heated Democratic primary. One senior Democratic official worried about Sestak’s electability still acknowledged that he holds even odds to win the nomination. And given the public’s growing distaste of establishment politicians, his outsider persona would certainly match the current political moment.

If Pennsylvania’s Senate primary offers a contrast in candidates’ backgrounds, the Florida race between two wildly differing congressmen—DSCC-backed Patrick Murphy and progressive pugilist Alan Grayson—will be a jarring contrast in ideology. Murphy is one of the most centrist Democratic officeholders in Congress, winning past support from the U.S. Chamber of Commerce. Because of that, party leaders view him as the most electable candidate to pick up a seat in a crucial battleground state. But Grayson, who has built a national profile thanks to his scathing, over-the-top attacks against Republicans, is betting that, like Trump, he’s the candidate that best appeals to the party’s base.

By the traditional metrics of fundraising and endorsements, the Senate primary in Maryland shouldn’t even be competitive. Rep. Chris Van Hollen raised nearly three times as much as Rep. Donna Edwards in the last fundraising quarter, and has been winning over the majority of Democratic elected officials in the state, including in her home county. For Van Hollen, being one of the House’s most influential Democrats as a past DCCC chairman and current ranking member on the Budget Committee usually confers political benefits. But Edwards is betting that her identity is a more powerful political asset than his influence.  In a state where a near-majority of Democratic voters are African-American, running to be the only black woman in the Senate carries clear appeal.  There are signs that her assumption is accurate: Her campaign released polling in August showing her leading Van Hollen by 5 points.

The other two notable Democratic primaries—in Ohio and Illinois—wouldn’t even be taking place if party leaders had more sway over their candidates. Democratic officials assumed that 30-year-old Cincinnati city councilman P.G. Sittenfeld, who entered Ohio's Senate race in January, would step aside if former Gov. Ted Strickland decided to run (which he did). Instead, Sittenfeld stuck to his plan and has been a persistent nuisance to Strickland, attacking the former governor over his advanced age and his flip-flopping on issues. He’s very unlikely to win, but the primary is worth keeping an eye on given the clear generational contrast. If the party’s voters want fresher faces, Strickland could have a tougher challenge than he anticipated.

In Illinois, Senate Minority Whip Dick Durbin worked to clear the primary field for Rep. Tammy Duckworth, an Iraq War veteran who looked like the strongest candidate to challenge Sen. Mark Kirk.  But former Chicago Urban League president Andrea Zopp didn’t get the message, and is hoping to rally African-American voters to her side in the primary. With the DSCC fully behind Duckworth, she’s a long shot, but her record as a business leader and attorney should give her enough credentials to get attention.

Since the start of the Obama administration, it’s the Republicans that have been badly divided and their factions have percolated in congressional primaries. For the most part, Democrats avoided the messy fate of their counterparts. But with the president leaving office, there are signs that the battle for the Democratic Party’s future is already under way. The results from the five competitive Senate primaries underway will go a long way in setting the stage for a post-Obama future.

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