By Rob Watson
BBC correspondent in Phoenix, Arizona
The American people who have watched these three presidential debates saw two starkly different candidates, both on politics and personality.
Snap polls suggested the third contest was a tie
George W Bush is a man who is clearly very passionate, conservative, and unilateralist in his foreign policy.
He is up against a more aloof John Kerry, clearly more liberal in his policies domestically, and more multilateralist in terms of his outlook towards the world.
Overall the debates have benefited the challenger more than the incumbent.
For Mr Kerry went into these debates some distance behind in the polls, and it looked like the president's election to lose.
Now, it is a dead heat.
In this third debate, both campaigns are very satisfied with the way that their candidates performed.
Both of them stuck to the strategies they had in mind.
Mr Kerry made a very biting critique of the Bush administration's record on a range of domestic policy - issues including the economy, health care and education.
He tried to portray the president as someone who was more worried about the rich folks in America - that he either did not care or was not aware of people who did not have health care or jobs.
Interestingly, Mr Bush came back very strongly, using a tactic he has tried to focus on over the last few months - making this election a referendum about John Kerry.
The president attacked Mr Kerry's record in the Senate and made that most explosive of all charges - and in recent years a very effective charge - that his opponent is a tax-and-spend liberal.
At one point, Mr Bush said the challenger was way off to the left of mainstream American politics.
In broad terms, Mr Kerry tried to make the case to voters that it is time for a change.
But he was quite careful to tick off all of the groups that he might need to win.
He made references to African-Americans, and appeals to women voters - both key constituencies. He even made references to Native Americans.
Bush's campaign believes he can win if personality is at the fore
The point has been made that George W Bush has directed his pitch much more to core Republican supporters, with very strong arguments against abortion and gay marriage.
But in the final debate, he was quite careful not to alienate undecided voters.
At several points he seemed much more concerned about those small number of people who are said to be in the middle.
The final days
From now on, the two candidates are going to be pouring their money and time into the 10 swing states where the race will be decided.
The campaigns will also put into operation incredibly sophisticated techniques for identifying their potential supporters.
It is not just a question of knocking on doors. This is hi-tech, with massive cross-referenced databases full of personal information about potential voters.
They will use this information to focus their efforts, to make sure that they get the most bang from the millions of bucks they will be spending.
The last thing, of course, is what the campaigns think will decide whether their investment sees a return.
The Kerry campaign believes that their man gets to win this election if the voters go into the polling booths on 2 November with Iraq and the economy on their minds.
On the other hand, the Bush campaign thinks that their man gets to win if the voters are thinking about the war on terror and personal qualities of the candidate such as leadership, strength and decisiveness.