In a more predictable election year, we probably wouldn't be spending so much time on congressional primaries where incumbents are the heavy favorites to win.
But this election is nothing if not unpredictable. As The Washington Post's Paul Kane reports, Republican congressional leaders will be closely watching how their candidates in states like North Carolina, Ohio and Illinois fair while sharing a ballot with Donald Trump. The question they'll be asking: Does Trump's (and to some degree Ted Cruz's) anti-Washington message hurt their lawmakers?
Democrats aren't immune to the anti-establishment vibe either. Sen. Bernie Sanders (I-Vt.) has the potential to upset Hillary Clinton in Midwestern states, so Democrats' chosen candidates to challenge GOP senators in November in those states may be more vulnerable to liberal challengers.
While all eyes are on the presidential contests, here are the seven other primary races to watch Tuesday, broken up into a few categories:
GOP incumbents hoping to avoid a surprise
Sen. Richard Shelby (R-Ala.) proved it can be done. In his March 1 primary, the 81-year-old longtime senator raised and spent millions to ensure that he bested an outsider challenger, even as Trump won his state by 25 points. The Republicans below are hoping for a similar victory, if not quite as costly or dramatic as Shelby's:
1. Sen. Richard Burr (N.C.): Nowhere is the establishment vs. anti-establishment dynamic perhaps clearer Tuesday than the North Carolina GOP Senate primary. Burr has spent the past decade in the Senate and is chairman of the powerful Intelligence Committee. It's not a stretch for his top rival, former congressional candidate Greg Brannon, to paint Burr as Washington establishment. Brannon even campaigns with a bus emblazoned with "Defeat the Washington Establishment" and is courting Trump and Cruz supporters.
A recent poll showed Burr well ahead of Brannon, and Jim Morrill and Tim Funk with the Charlotte Observer haven't uncovered any groundswell of anti-establishment fervor that suggests that what's happening on the presidential level could filter down to the Senate. But Burr isn't taking much for granted; he ended 2015 with $6 million in the bank and spent at least $300,000 on TV ads to highlight his "trusted conservative leadership."
2. Rep. John Shimkus (Ill.): The primary for Illinois's 15th Congressional District is a classic case of a tea party challenger trying to unseat a pro-business Republican.
For the first time in his 20-year congressional career, Shimkus is facing a GOP challenger. State Sen. Kyle McCarter uses buzzwords like "cushy careerist" to describe Shimkus, whom he accuses of not being conservative enough. Exhibit A in his argument is Shimkus's support for the spending bill Congress approved last December with the help of Democrats. This race got more interesting in January, when the grassroots conservative group Club for Growth endorsed McCarter over Shimkus. It has spent a not-insignificant $280,000 to get him elected.
Shimkus, meanwhile, has almost 10 times the cash advantage, plus the endorsements of the U.S. Chamber of Commerce, National Right to Life and the National Rifle Association. Illinois's GOP governor, Bruce Rauner, has also been on the trail for Shimkus.
3. Sen. Rob Portman (Ohio): Portman's biggest obstacle in winning a second term in the Senate will be November's reelection, where his seat is seventh on The Fix's most recent list of top 10 most vulnerable. (Senate Democrats are hoping to tie incumbents like Portman to Trump's more divisive comments with web ads like this one they just released.)
To gauge how well he'll do in November in the face of those attacks, Senate Republicans will be watching Portman's margin against little-known challenger Don Elijah Eckhart, a Christian conservative who is staking his campaign on Portman's support for same-sex marriage. Portman has cited his gay son for his break from the Republican Party on this issue.
Going into his primary, he's fresh off the Senate approving an opioid epidemic aid package he co-sponsored, and the Senate is closing in on a deal he co-sponsored to provide loans for communities affected by lead-tainted water, including one in Ohio. Portman has $13 million in the bank, but he's saving most of that for the general election -- suggesting he's confident about winning easily Tuesday.
Democratic challengers hoping to avoid a surprise
In November, Democrats are hoping to challenge several of Senate Republicans' most vulnerable members. But to do that, they've got to get through their own primaries, which have an anti-establishment tinge to them as well.
4. Illinois: If Illinois's Senate race is one of the marquee races for Senate Democrats this cycle, their primary is also drawing some national attention.
Two-term Rep. Tammy Duckworth is the odds-on favorite to win a three-way primary against former Chicago Urban League CEO Andrea Zopp and state Sen. Napoleon Harris, a former NFL player.
A recent Chicago Tribune poll shows Duckworth with 72 percent of support, compared to 8 percent for Zopp and 4 percent with Harris, with another 16 percent undecided. Duckworth holds a 3-to-1 advantage among African American voters -- a voter base Zopp, who is black, was counting on. What's more, 9 out of 10 voters know Duckworth, in part thanks to her compelling life story: She lost both legs after being shot down as a U.S. Army helicopter pilot in Iraq in 2004.
But Illinois Democrats say they are expecting the well-connected Zopp, who is a former prosecutor, to do better than polls suggest. She has the endorsement of newspapers like the Chicago Sun-Times (Duckworth has the Chicago Tribune) and the support of the Rev. Jesse Jackson.
5. Ohio: Former governor Ted Strickland is the favorite to win Tuesday's Senate primary against an energetic 31-year-old Cincinnati councilman, P.G. Sittenfeld. (There's another challenger, little-known occupational therapist Kelli Prather, who's trying to be Ohio's first woman and first African American senator.)
Sittenfeld's campaign has gained some traction, in part because of who his opponent is, but polling suggests it won't be enough to upset a former governor. In March, President Obama and Vice President Biden endorsed Strickland. Senate Democrats are really watching Strickland's win margin here to see how his message plays with the base after being out of office for five years. (Strickland lost to now-Gov. John Kasich in 2010.)
6. North Carolina: Senate Democrats' choice to take on Burr is a first-time statewide candidate, former state representative Deborah Ross, who is lining up to have a good showing in her three-way primary. She has raised some $920,000 so far and has the endorsements of the Planned Parenthood and Emily's List. Her less-well-financed opponents are businessman Kevin Griffin -- who has been campaigning at Sanders's North Carolina rallies -- and Spring Lake Mayor Chris Rey.
The Fix does not have North Carolina on its most recent rankings of the top 10 Senate races most likely to flip, but that could change depending on Ross's performance Tuesday and beyond.
Republicans battling it out for a symbolic victory
7. John Boehner's seat: After one man held Ohio's eighth congressional seat for nearly a quarter of a century, no fewer than 17 Republicans are trying to take it next. And tea party backers are keen on a symbolic win here.
As Politico's Theodoric Meyer reports, voters in the district seem torn about whether the next lawmakers should follow in the former Republican speaker's footsteps or go an entirely different path. That seems to be setting up the battle lines; the Club for Growth is spending more than $1 million on TV ads backing tea party-aligned candidate Warren Davidson and attacking his rivals. Former Ohio GOP Rep. Steve LaTourette, a moderate Boehner ally, has a Super PAC, Defending Main Street, that aims to block a candidate like Davidson from taking the seat. Meanwhile, a new movement, the Right Way Initiative, is getting involved to the tune of $450,000 on ads for the more moderate state Rep. Tim Derickson.
The district is so solidly Republican that the winner Tuesday is likely to represent the seat in Congress in January. Whether it's tea party candidate or a more mainstream one could give either side momentum going into this year's intra-party budget battles in the House of Representatives.
Not voting: North Carolina House primaries
Two of North Carolina's House districts are caught up in a gerrymandering drama that has pushed back primaries for all 13 House districts.
A three-judge federal court panel ruled two majority-black districts are an example of unconstitutional racial gerrymandering and must be redrawn. In February, the U.S. Supreme Court rejected a request to essentially wait to redraw the districts after the state's primary Tuesday. So the GOP-controlled state legislature was forced to push back the states House primaries to June while it agrees to new lines.
Candidates will still appear on Tuesday's ballot, but any votes cast for them won't count.