Following weeks of relative calm in the primary election schedule, voters in four states will pick nominees Tuesday for a range of critical midterm election races.
In a fifth — Ohio — a special election in a reliably red district will send a new member to Congress for only a few months. But the race outside of Columbus has bigger stakes as a measure of how concerned Republicans should be about defending their House majority in November.
Here are the key contests to watch across the country on Tuesday:
In red Kansas, President Donald Trump has a chance to disrupt what should be a relatively smooth gubernatorial race for his Republican Party. On Monday, the president endorsed Kansas Secretary of State Kris Kobach over incumbent Gov. Jeff Colyer in the GOP primary. Kobach was one of the biggest proponents of Trump's repeated, unproven claims of widespread voter fraud in the 2016 election.
He became a member of Trump's voter fraud commission, which even numerous Republican secretaries of State slammed last year before it was disbanded. If he wins the primary, it could make November's general election competitive despite the fact that Trump carried the state by about 20 percentage points in 2016.
In a tweet Monday, Trump called Kobach "a strong and early supporter" who "will be a GREAT governor."
On the Democratic primary side, a crowded field includes state Sen. Laura Kelly and former Wichita Mayor Carl Brewer.
Two GOP-held House seats in Kansas could also be competitive in November as Democrats try to flip the 23 GOP seats needed to take a House majority. In the 3rd District, multiple Democratic candidates aim to challenge Republican Rep. Kevin Yoder. The race is among a few primaries Tuesday that will test whether Midwestern Democrats prefer candidates who champion progressive policies, or those considered more centrist and better able to compete in a general election for a swing seat.
In Kansas' 2nd District, Democrat Paul Davis runs unopposed as he tries to flip a red seat vacated by GOP Rep. Lynn Jenkins' retirement. In a crowded Republican field, leading candidates include state Sens. Steve Fitzgerald and Caryn Tyson.
Michigan is one of the 10 states that Trump won in 2016 where a Democratic senator faces re-election this year. For now, Democratic Sen. Debbie Stabenow appears pretty safe in a state the president carried by less than a percentage point.
Trump endorsed Army veteran John James in the Republican primary to challenge Stabenow, calling him a "potential Republican Star." Trump predicted that James would beat Stabenow — but early polls of potential general election matchups show the incumbent with a comfortable edge over both James and businessman Sandy Pensler, another top contender in the GOP primary.
The state also has two House races and a gubernatorial contest expected to be tight in November. Former Obama administration Defense Department official Elissa Slotkin will face Michigan State University professor Chris Smith in the Democratic primary for Michigan's 8th District. The winner will take on GOP Rep. Mike Bishop in a race that nonpartisan election analysts consider a toss-up.
Another toss-up race will take place in Michigan's 11th District. Republican Rep. Dave Trott's retirement opened up the seat. The primary is crowded on both the Republican and Democratic sides as about 10 candidates total vie for the office.
The race for Michigan governor will test the direction of both major parties in the Midwest. On the Democratic side, former state Sen. Gretchen Whitmer faces off against public health official Abdul El-Sayed and entrepreneur Shri Thanedar. El-Sayed has tried to capture Michigan's progressive wing: both Sen. Bernie Sanders, I-Vt., and New York City-area Democratic congressional nominee Alexandria Ocasio-Cortez have campaigned for him.
Republican Gov. Rick Snyder, considered a more moderate GOP official than the president, is term limited. Trump has endorsed state Attorney General Bill Schuette in the GOP gubernatorial primary. His opponents include Lt. Gov. Brian Calley.
Missouri holds one of the most important Senate races of the year. Democratic Sen. Claire McCaskill, one of the most vulnerable members of the chamber, runs for re-election in a state Trump won by nearly 20 percentage points.
The contest is among a handful that will determine whether Republicans can keep or expand their 51-49 seat majority in the Senate. Missouri Secretary of State Josh Hawley is a heavy favorite in Tuesday's GOP primary. Early polls have shown a neck-and-neck general election contest between McCaskill and Hawley.
None of the year's most competitive House races will take place in Missouri. However, another self-described progressive in Missouri's 1st District will try to replicate Ocasio-Cortez's success in taking down a longtime incumbent Democrat.
Community activist Cori Bush hopes to beat Rep. William Lacy Clay to win the heavily blue St. Louis seat.
Outside of Columbus, a special election for a longtime Republican House seat may give more clues about what to expect from the country's electorate in November's midterm elections. Democrat Danny O'Connor, the 31-year-old Franklin County recorder, hopes to beat Republican state Sen. Troy Balderson and flip a seat the GOP has held for more than 30 years.
Fearing a second special election debacle this year, national Republicans have spent heavily to oppose O'Connor. Both Trump and Vice President Mike Pence also came to the district late in the race to try to boost Balderson.
A pair of House races in Washington state will be watched closely in November. Nonpartisan election analysts consider the 8th District seat vacated by GOP Rep. Dave Reichert's retirement a toss-up.
Democrats also hope to challenge one of the highest-ranking Republicans in Congress: Rep. Cathy McMorris Rodgers in Washington's 5th District.
The state has a primary system in which the top two candidates regardless of party qualify for the general election. State Sen. Dino Rossi, a Republican, is expected to take one of those spots in the 8th District, leaving top Democratic contenders Kim Schrier and Shannon Hader — both doctors — and lawyer Jason Rittereiser to battle for the second spot.
Former state lawmaker and educator Lisa Brown is favored to take on McMorris Rodgers in the 5th District.