[an error occurred while processing this directive]All the seats in the House of Representatives are up for grabs as well as a third of the Senate.

The governorships of 36 states, including California and Texas, are also being contested.

The elections provide US voters with their first opportunity to give their verdict on President Clinton since the emergence of the Monica Lewinsky scandal.

BBC Washington Correspondent Bridget Kendall: Despite the Lewinsky scandal, the Democrats may do well

Most predictions have the Republicans, who hold majorities in both houses of Congress, gaining a few seats.

However, last-minute polls suggest the Democrats could produce some surprises, especially if there is high turnout among their black supporters.

The Lewinsky factor

President Clinton: Impeachment worries

Washington Correspondent Paul Reynolds says that overall, the election campaign has been lacklustre, with the Lewinsky scandal not playing as prominent part as had initially been expected.

Democrats have suggested that a last-minute Republican advertisement campaign which included veiled references to the Lewinsky scandal might have backfired, by shaking Democrat voters out of their apathy.

However close the race may be, commentators are suggesting that the outcome will have an impact on the impeachment proceedings faced by Mr Clinton.

Katty Kay: It has been called the election about nothing

Republican gains would be likely to give the party the confidence to push ahead quickly with impeachment in Congress.

A swing to the Democrats would have the opposite effect and would bolster the president's position.