Voting is underway in United States for Tuesday’s pivotal midterm elections, with all 435 House of Representatives seats and 35 of the Senate’s 100 seats being contested. Polls are open in all 50 states.

More than 57 million Americans have already cast early ballots, with some of the heaviest voting coming from some of this year’s biggest political battlegrounds: Georgia, Michigan, North Carolina, Ohio and Texas.

Voters in 36 states will also elect governors.

Republicans currently have a majority (53) in the 100-seat Senate. Democrats and independents who caucus with the party hold 47. Republicans also have a narrow four-seat majority in the House.

Democrats have campaigned on promises to address the nation’s cost-of-living crisis and end Trump’s war on Iran.

They are eyeing historic gains in both houses of Congress that could ultimately change the trajectory of the US president’s final two years in office.

Republicans, however, are hoping to defy political gravity.

Despite Trump’s near record-low approval ratings and a historical precedent for significant midterm losses by the sitting US president’s party, conservative and right-leaning candidates are banking on their most loyal voters and distrust of progressive politics to help turn the tide on Democrats’ expected gains.

Tuesday’s midterms also come on the back of Haley Stevens, who lost Michigan’s Democratic Senate primary in August, endorsing Republican Mike Rogers over her party’s nominee, Abdul El-Sayed, on Sunday.

After voting had began in a majority of states, the US Department of Justice announced that it was deploying about 1,000 election monitors to observe polling. It is the first time that monitors have been deployed to all 50 states.

“I am very proud we are deploying the largest monitoring effort in DOJ history, and pursuing transparency for elections in an assertive and nondiscriminatory manner,” said Assistant Attorney General Harmeet K. Dhillon of the civil rights division at the DOJ.