Four states are hosting primaries Tuesday, which will decide the matchups in several contested House races and two Senate races.

Voters in Missouri, Kansas and Michigan will head to the polls, while Washington voters will head to their mailboxes, to choose nominees in a slew of competitive races. 

The day will also see the final House special election before November, with Republican Troy Balderson and Democrat Danny O’Connor facing off in Ohio’s 12th District. Here are four things to watch among the primary races:

1. GOP seats Clinton won

Democrats will choose nominees in a number of targeted races Tuesday, including two districts that Hillary Clinton carried in 2016.

In Washington’s open 8th District, former GOP state Sen. Dino Rossi is a favorite to finish first in the primary, while three Democrats are seen as leading contenders to join him on the November ballot. (Under the state’s primary system, all candidates run on the same ballot with the top two vote-getters, regardless of party, advancing to the general election.) GOP Rep. Dave Reichert is retiring after representing the district, which includes the Seattle suburbs and farm country, for seven terms. Voters here backed Clinton by 3 points in 2016 and Inside Elections with Nathan L. Gonzales rates the race a Toss-up.

While Republicans have coalesced around Rossi, it’s not clear which Democrat will take second place. Female Democratic challengers could dominate the targeted races in Washington, including the 8th District. The Democrats to watch are pediatrician Kim Schrier, who has been endorsed by EMILY’s List, prosecutor Jason Rittereiser, and Shannon Hader, a physician who led a global division at the Centers for Disease Control and Prevention. The results here might not be known for some time, if it’s close. Washingtonians vote by mail, and ballots have to be postmarked by Election Day or dropped in a box by 8 p.m. Pacific time.  

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Kansas’ 3rd District, hed by GOP Rep. Kevin Yoder, is another top suburban target for Democrats. Republicans appeared to be meddling in this Democratic primary in the final days, with the GOP group Ending Spending launching a television ad that appeared to cast Democrat Brent Welder in a positive light. Welder has been endorsed by Sen. Bernie Sanders and Alexandria Ocasio-Cortez, who unseated House Democratic Caucus Chairman Joseph Crowley in New York in June. Welder has been branded as the candidate furthest to the left with his support for “Medicare for All” legislation and a $15 minimum wage.

Welder is part of a crowded field of Democrats fighting to take on Yoder, with operatives agreeing he’s a top contender along with high school teacher Tom Niermann, and Sharice Davids, a lawyer and former MMA fighter who has been endorsed by EMILY’s List. National Democrats believe any of those three candidates would be a strong challenger to Yoder. Inside Elections rates the race Leans Republican.

2. Other Democratic targets

Kansas GOP Rep. Lynn Jenkins’ decision to retire opened up her 2nd District seat, where Democrats believe they have a strong contender in former state House Minority Leader Paul Davis. He carried the district when he ran unsuccessfully for governor in 2014. Davis was also among the first Democratic candidates to say he would not support Nancy Pelosi for leader. 

A crowded field of seven Republicans are vying for the GOP nod. Some believe Steve Watkins, an Afghanistan War veteran, could have an edge as a political outsider — he’s the only one who hasn’t held elected office. And he’s had some help from a super PAC founded by his father. State Sen. Caryn Tyson had the most cash on hand at the end of the pre-primary period, followed by fellow state senator and Army veteran Steve Fitzgerald. Inside Elections rates the race Leans Republican.

Democrats are targeting a handful of districts in Michigan. In two of those races, the Democratic Congressional Campaign Committee picked early favorites, adding Gretchen Driskell in the 7th District and Elissa Slotkin in the 8th to its Red to Blue program for top recruits. Both are expected to easily win their primaries, with Driskell likely facing the steeper climb in November. She lost to GOP Rep. Tim Walberg by 15 points in 2016, and is giving it another shot in a Likely Republican race. Meanwhile, Slotkin, a former acting assistant secretary of Defense, would face GOP Rep. Mike Bishop in a Leans Republican race.The House Democrats’ campaign arm has stayed out of the 11th District, but one national party figure hasn’t. Clinton over the weekend endorsed Haley Stevens, who was chief of staff for former President Barack Obama’s Auto Task Force. She’s running in a five-way primary for the Democratic nomination for the seat GOP Rep. Dave Trott is vacating. Clinton followed up Monday night with a robocall for Stevens.Also seeking the Democratic nod in the 11th are tech CEO Suneel Gupta (the brother of CNN’s Sanjay Gupta), state Rep. Tim Greimel, former Obama official Fayrouz Saad, who’s also the former director of immigration affairs for Detroit, and radio talk show host Nancy Skinner, who’s run for this seat before but hasn’t raised or spent any money this time. Gupta had raised the most money by the end of the pre-primary reporting period (including a $150,000 personal loan) and ended with the most cash on hand. In addition to winning the nomination, Saad is trying to become the first Muslim woman elected to Congress.

On the GOP side, businesswoman and former Trump campaign state co-chair Lena Epstein has amassed the biggest war chest (she loaned her campaign $990,000) and attracted the most attention. The National Republican Congressional Committee has named her to the lowest level of its Young Guns program. She’ll have to fend off four other Republicans, including former Rep. Kerry Bentivolio, who ended the pre-primary period with $800 in the bank. The 11th District race will likely be competitive heading into November, with Inside Elections rating it a Toss-up.  

Democrats are also targeting Michigan’s 6th District, which is held by GOP Rep. Fred Upton. The four-way primary has come down to a race between physician and former YMCA National Health Director Matt Longjohn and George Franklin, the former vice president of government relations at Kellog. They’ve raised similar amounts of money, with Longjohn loaning his campaign about $70,000. Inside Elections rates the race Likely Republican.

The Democratic path in the 1st District, another DCCC-targeted seat, is a little more complicated. Iraq War veteran Matt Morgan is waging a write-in campaign to get on the ballot as the Democratic nominee because he was disqualified for listing a post office box, instead of his home address, on his initial petitions. Inside Elections rates the race Solid Republican.

3. Democratic infighting

Democratic divisions are playing out in primaries in three safe seats Tuesday. In Missouri’s 1st District, Rep. William Lacy Clay is facing nurse and activist Cori Bush in what could be his closest primary yet. Bush, who organized protests in Ferguson, has also been endorsed by Ocasio-Cortez, and is running a similar campaign with a bold, progressive agenda that is focused on energizing new and younger voters. But some Democrats still expect Clay to win thanks to his turnout apparatus and high name recognition. And unlike Crowley’s race, the demographics in this St. Louis-based district haven’t fundamentally shifted since Clay took office.

Two solid blue open seats in Michigan have also led to Democratic warring. Three Democrats are running for the nomination in the 9th District, currently held by retiring 18-term Rep. Sander M. Levin. One of them is Levin’s son, Andy. He’s running against former state Rep. Ellen Lipton, who has the backing of EMILY’s List. Having loaned her campaign about $290,000, she has slightly more money than Levin. Family feuding has featured in the race for the 13th District, which opened after former Rep. John Conyers Jr. stepped down late last year over allegations of sexual harassment. Conyers had endorsed his son, John Conyers III, to replace him, but he did not make the final ballot. Ian Conyers, the great-nephew of the disgraced lawmaker, who is also running, took steps to have John Conyers III kicked off the ballot for not collecting the requisite number of signatures from people registered to vote in the district. Ian Conyers is running against five other Democrats, including former state Rep. Rashida Tlaib, the first Muslim woman elected to the Michigan Legislature, who could also be the first Muslim woman elected to Congress. She’s raised and spent the most money.

4. Senate GOP challengers

Two Republicans could discover the strength of President Donald Trump’s endorsement Tuesday. In Missouri, Trump said he supported Attorney General Josh Hawley back in November, but Hawley still faces 10 other Republicans on the GOP primary ballot. His top competitors are former Libertarian presidential candidate Austin Petersen and Air Force veteran Tony Monetti. Hawley is nevertheless expected to come through to face Democratic Sen. Claire McCaskill, who is one of the most vulnerable incumbents this year. McCaskill faces six Democratic primary challengers Tuesday, but none have raised more than $1,000. Inside Elections rates the Senate race a Toss-up.And in Michigan, Trump endorsed businessman and Iraq War veteran John James late last month in the race to take on Democratic Sen. Debbie Stabenow in a Solid Democratic race. National Republicans say James may have a slight advantage over businessman Sandy Pensler, with the president’s endorsement helping to mitigate any spending disadvantage he had.