Polls began closing Tuesday in New Hampshire's pivotal Senate primary, where four-term Democratic Rep. Chris Pappas faces a challenge from the left by Karishma Manzur, a socialist-aligned candidate.

The Democratic nomination contest is being closely watched as it could influence which party controls the Senate in the upcoming midterm elections. Republicans have not won a Senate seat in New Hampshire in 16 years, but see the open seat as a key opportunity.

Manzur, a scientist with a Ph.D. in biochemistry and a nonprofit leader, has gained traction by advocating for policies such as universal healthcare, raising the minimum wage to $20 per hour, abolishing ICE, and ending military aid to Israel, which she has criticized over the conflict with Hamas.

She has characterized Pappas as a "genocide enabler" for his support from pro-Israel groups and argued that he has not adequately served his constituents. Pappas, who has held the Senate frontrunner position since Sen. Jeanne Shaheen announced her retirement, defended his record by stating he has been fighting to remove big money from politics since his election to Congress in 2018. He emphasized his appeal to pragmatic voters in the state.

Pappas, in an interview, defended the U.S.-Israel relationship, stating, "Israel's a historic ally of the United States, the only democracy in the region." He also expressed disagreement with Israeli Prime Minister Benjamin Netanyahu's current approach.

Meanwhile, the Republican Senate primary is characterized by a battle for influence stemming from former President Donald Trump's endorsement. Trump backed John E. Sununu, a former senator and Trump critic, over Scott Brown, another former senator and one of Trump's former ambassadors.

Sununu has received support from Senate Majority Leader John Thune and the National Republican Senatorial Committee. Brown has criticized Sununu for not publicly embracing Trump's endorsement and argued that Sununu is beholden to Washington leadership rather than the people of New Hampshire. Sununu, however, focused on his local endorsements and grassroots support.

In other races, Stefany Shaheen, daughter of the retiring Sen. Jeanne Shaheen, is in a contest for the Democratic nomination in New Hampshire's 1st Congressional District against Maura Sullivan and progressive contender Carleigh Beriont. The Republican nomination in that district features businessman Anthony DiLorenzo, backed by Trump, and businesswoman Hollie Noveletsky.

In the 2nd Congressional District, first-term Democratic Rep. Maggie Goodlander faces a primary challenge from state Rep. Paige Beauchemin. Lily Tang Williams is the frontrunner in the Republican primary for that seat.

Republican Gov. Kelly Ayotte is running for a second term with no significant opposition, while Cinde Warmington is unopposed for the Democratic gubernatorial nomination.