President Donald Trump has urged voters to back the Republican Party on the eve of the midterm elections.
He said during a blitz of three final rallies: “Everything we have achieved is at stake tomorrow.”
The November 6 vote is being seen as a referendum on Donald Trump’s presidency.
The president’s ability to govern in the final two years of his term will hinge upon the outcome.
Americans are going to the polls to vote on all 435 seats in the House, 35 of the 100 Senate seats and dozens of state governors.
With the control of Congress up for grabs, President Trump has ratcheted up rhetoric on divisive issues in a bid to energize his base.
Meanwhile, former President Barack Obama campaigned for the Democratic Party.
He tweeted: “Tomorrow’s elections might be the most important of our lifetimes. The health care of millions is on the ballot. Making sure working families get a fair shake is on the ballot. The character of our country is on the ballot.”
The midterm elections will decide which party will control the two houses of Congress.
If Republicans maintain their hold on the Senate and the House of Representatives, they could build on their agenda and that of President Trump.
If the Democrats wrest control of one or both chambers, they could stymie or even reverse President Trump’s plans.
Pollsters suggest Democrats may win the 23 seats they need to take over the House of Representatives, and possibly 15 or so extra seats.
However, the Democrats are expected to fall short of the two seats they need to win control of the Senate.
Governors are also being chosen in 36 out of 50 states.
After months of campaigning, speculation, and billions of dollars spent on adverts, leaflets and bumper stickers, voters will have their final say on November 6.
Democratic candidates for the House of Representative have raised $649 million from individual donors, more than doubling the $312 million tally for the Republicans.
Democrats are hoping to achieve a “midterm wave” – a sweeping victory that changes the shape of the political map in the US.
Many people have already voted.
The US Elections Project, a University of Florida-based information source, said that some 34.3 million people have cast early ballots but the real number is probably higher. In 2014, were just 27.5 million.
In Texas, early voting has exceeded the entire turnout in 2014.
Thunderstorms are forecast for November 6 along the eastern coast, as well as snowstorms in the Midwest, which could affect turnout.
The first polls close at 18:00 EST.