Primary elections are taking place Tuesday in Maine, South Carolina, Nevada and North Dakota, featuring contested races for governor and congressional positions that will help settle ballots for November’s general election.

Republicans in several states are dealing with retirements and intraparty challenges, while Democrats are looking to take advantage of fissures in the GOP and hold onto moderate seats in red districts.

Here’s what to keep an eye on as results roll out.

Maine Voters Face Many Options 

One of the most widely discussed races Tuesday pits Gov. Janet Mills against embattled oyster farmer Graham Platner for the Democratic nomination in the U.S. Senate contest against longtime incumbent Republican Sen. Susan Collins. The nomination seemed all but certain for Platner after Mills dropped out of active campaigning in April. But new accusations of infidelity and abusive behavior toward past girlfriends have emerged against Platner, leading Mills to recently remind Maine voters that her name remains on the ballot.

Mills’ term-limited seat is up for grabs in a state that’s consistently elected leaders from either party. The current front-runner among five gubernatorial candidates, Dr. Nirav Shah, garnered name recognition as the head of Maine’s Center for Disease Control and Prevention during the COVID-19 pandemic. But energy executive Angus King III, the son of former Sen. Angus King, isn’t far behind.

The Republican primary is equally crammed with seven candidates. Former Assistant Secretary of State Robert Charles appears to be leading the way in that race.

In the House, Democratic incumbent Rep. Jared Golden created a competitive race after announcing he would not run for reelection in Maine’s 2nd District. The race, in what historically has been a red-leaning area of Maine, could become a chance for Republicans to gain a seat in an otherwise challenging midterm for them.

State Sen. Joe Baldacci appeared to be the clear Democratic front-runner for much of the race, but recent polling shows a tight race between him, state auditor Matt Dunlap and Jordan Wood, the former chief of staff to California Rep. Katie Porter.

The winner of the Democratic primary will face former Maine Gov. Paul LePage in November.

Republican Rifts in South Carolina 

President Donald Trump overlooked longtime ally Rep. Nancy Mace to endorse Lt. Gov. Pamela Evette, effectively boosting the latter to the front-runner position in the last few weeks of polling.

Mace took to social media to call Evette’s endorsement fake, writing, “Do not believe her LIES” above an artificial intelligence-generated video of herself and Trump posing together.

In the Senate, incumbent Republican Lindsey Graham faces challengers from within the GOP. A South Carolina senator for over two decades, Graham is facing criticism from fellow Republicans over his frequent breaks in party-line votes. Although Graham still leads in polling and has Trump’s endorsement, businessman Mark Lynch has gained a modest amount of traction.

Despite little chance for statewide Democratic success, three candidates will face off in the party’s Senate primary. Front-runner and pediatrician Annie Andrews might be familiar to voters from her loss against Mace in the 2024 election.

Nevada’s Historic House Race 

After a surprising retirement announcement from Rep. Mark Amodei, Nevada’s 2nd District seat will see its first contested race in over 15 years. Trump recently endorsed retired Lt. Col. David Flippo, going against Amodei and Gov. Joe Lombardo’s endorsements of state Sen. James Settelmeyer.

Flippo is currently outpacing Settelmeyer in spending both through self-funding and donations from the Freedom Caucus Fund, which represents hard-line conservative House members.

In the race for governor, the eventual Democratic candidate will face a battle with the conservative Lombardo. In the lead is Aaron Ford, Nevada’s first Black attorney general. But County Commissioner Alexis Hill is running on an anti-billionaire platform, similar to the one that proved successful for New York City Mayor Zohran Mamdani.

North Dakota House Seat Might Change Hands 

A red state with just one House seat, Democrats are looking to clinch a win against incumbent Republican Rep. Julie Fedorchak. But she’s threatened by challenges within her own party, too – most notably from veteran Alex Balazs, who boasts the state GOP’s endorsement. Fedorchak won the Republican primary in 2024 with just 46% of the vote, making her a vulnerable candidate.