In the mid-term elections, 35 of the 100 seats in the Senate will be up for grabs. All 435 seats in the House of Representatives will be filled. According to polls, ex-President Donald Trump's Republicans are likely to wrest their majority in the House of Representatives from President Joe Biden's Democrats. The conservatives also have a good chance of taking control of the Senate, where the Democrats have so far held a razor-thin majority.

However, several Senate races in states such as Arizona, Pennsylvania, Nevada and Georgia are extremely close. It could take days -- and even a month in Georgia given a runoff rule -- for the results to be known.

In the House of Representatives, the winner could still be determined on election night. But even that is not certain. The governors of 36 of the 50 US states were also elected on Tuesday.