The elections will see voting for 35 of the 100 seats in the Senate and all 435 seats in the House of Representatives.
Around 210 million Americans are expected to be eligible to cast their ballots, while more than 50 million voters have already voted in person or by mail ahead of Election Day.
The results will determine the political balance in Congress for the remainder of Trump’s current presidential term. If Democrats secure a majority in the House of Representatives, they could place greater constraints on the president’s legislative agenda and exercise stronger oversight of his administration.
Republicans currently hold a 53-47 majority in the Senate and also have a narrow advantage in the House of Representatives.
In addition to congressional races, voters in 36 states will elect their governors, making the midterm elections significant at both the federal and state levels.
The White House has reportedly prepared a political strategy in case Republicans suffer losses, as the outcome could affect the administration’s ability to advance its legislative priorities.
The elections are being closely watched because control of Congress will shape the relationship between the White House and lawmakers, as well as the direction of US domestic policy over the next two years.