Americans vote today in elections which will also help decide the outcome of the impeachment inquiry into President Clinton.
Strong Republican gains, which would normally be expected in these mid-term elections, would make it more likely that Mr Clinton would face impeachment in the next Congress.
But if Republicans win only a small number of seats or even lose some, Democrats will be encouraged to fight harder to end the impeachment process, which is unpopular with the majority of voters.
At stake in the election are all 435 seats in the House of Representatives, 34 seats in the 100-member Senate, 36 governorships and thousands of posts at state and county level.
Also on the ballot in a number of states are referendums on issues ranging from the legalisation of marijuana for medical purposes to same sex marriage and the sale of horse meat.
At present the Republicans have a small majority in both the House and the Senate. A net gain of 11 seats would give Democrats a majority in the House, but most observers expect the Republicans to hold on to their control of both houses in Congress.
Democrats are slightly ahead in the latest polls based on voters' intentions in Congressional districts. The Pew Research Centre poll shows Democrats leading Republicans by 46 per cent to 44 per cent.
A Gallup poll for USA Today/CNN gives Democrats 48 per cent and Republicans 45 per cent. However, a Fox News poll gives Republicans a slight lead among those "most likely to vote".
A low turn-out would hurt Democrats as Republican voters tend to be more highly motivated. An appeal for a high turn-out was heard from space from Democratic Senator John Glenn who is orbiting the earth in the Discovery space shuttle.
Some experts anticipate one of the lowest turn-outs on record because of the lack of any burning issues to energise the voters at a time of economic prosperity. It could be as low as 35 per cent.
Republicans have been disappointed at the lack of impact on the election campaign of Mr Clinton's affair with Ms Monica Lewinsky and the allegations in the Starr report that he perjured himself and obstructed justice.
It is only in the closing stages of the campaign that the Republicans have resorted to TV advertisements in a $10 million splurge in 14 states reminding voters about how he denied the affair for eight months.
"Should we reward not telling the truth?" one ad asks. "That is the question of this election. Reward Bill Clinton. Or vote Republican."
The President has avoided the kind of high-profile campaigning that he normally undertakes in elections. Instead he has concentrated on fund-raising with Democratic audiences and televised ceremonies from the White House showing him in a presidential role.
Vice-President Al Gore and Mrs Hillary Clinton have campaigned across the country for Democratic candidates in danger in areas like California, Chicago and New York. The President has in recent days concentrated on encouraging African-Americans, who usually support Democrats, to come out and vote. Their support and that of women voters could swing some crucial contests.