Vice-President Al Gore and Governor George Bush face their third and last television debate tonight in St Louis just three weeks away from the US presidential election.
While the momentum has shifted to Mr Bush since the first two debates, political observers say that this election is the closest since John F. Kennedy defeated Richard Nixon in 1960 by less than one per cent of the popular vote.
The CNN/USA Today daily tracking poll showed Mr Bush continuing to have a three percentage-point lead over Mr Gore by 48 to 45. The Reuters tracking poll showed Mr Bush's three-point lead narrowing to one point.
There are conflicting estimates on which candidate is ahead in the electoral college which actually elects the winner based on the returns from each of the 50 states. A majority of 270 votes by the electoral college is needed for victory.
Based on state-by-state opinion polls, USA Today estimates that Mr Gore has a lead of 171 electoral votes to 153 for Mr Bush. This is in the 11 states where Mr Gore's lead in the state polls is greater than the margin of error. These include the highly populated states of California, New York, New Jersey and Illinois, which between them have 124 electoral votes.
Mr Bush's tally of 153 is based on the 19 states where his lead in the polls is greater than the margin of error. The bulk of these are low density population states in the Rocky Mountains and the south with small numbers of electoral votes. The exception is Texas with 32 votes which is safe for Mr Bush as his home state.
The other 20 states are seen as too close to call but Florida with 25 electoral votes and Pennsylvania with 23 are battleground states which both campaigns are fighting hard to win.
The conservative Washington Times estimates that Mr Bush is leading in electoral votes by 239 to 189 if the tally includes a category called "leaning for Bush" and "leaning for Gore".
There appears to be a greater air of confidence in the Bush camp following his better than expected performances in the first two debates against Mr Gore, who had the reputation of demolishing his opponents in previous elections. But observers are warning that the Bush camp suffered from over-confidence before the New Hampshire primary, where Mr Bush was routed by Senator John McCain.
Mr Gore has been continuing his attacks on Mr Bush's record on healthcare in Texas, which he says is one of the worst in the country. Mr Gore used this issue effectively in the second debate where he put Mr Bush on the defensive and is expected to press home his attack in tonight's debate.
The format for the debate is that of a "town hall meeting" where the two candidates will be allowed to walk around the stage while taking questions from the audience. This is a format which Mr Gore has used continuously during his campaign.
Readers can view a recording of the presidential debate from 1 a.m. (Irish time) tomorrow, and read Joe Carroll's analysis on The Irish Times US Election website on www.ireland.com from early tomorrow morning.