In both Virginia and New Jersey, the campaigns have been very personal, very nasty - and very close. In the former, the Republican candidate Jerry Kilgore and his Democratic opponent, the outgoing lieutenant governor, Tim Kaine, are neck and neck; in New Jersey, the current US Senator Jon Korzine holds a slim lead over his opponent, the Republican businessman Doug Forrester, after spending a record $70m (£40m).
There are several other high-profile votes tomorrow - among them an expected comfortable victory for Michael Bloomberg in his bid for a second term as New York's mayor, and the four ballot initiatives in California backed by the state's struggling Governor, Arnold Schwarzenegger. But national political attention is focused on the two gubernatorial battles.
In both states, negative advertising has swamped the airwaves. Seeking to exploit the popularity of the death penalty in Virginia (which executes more people than any state save Texas), Mr Kilgore has shown television spots accusing Mr Kaine, an opponent of capital punishment, of "saying that Adolf Hitler doesn't qualify for the death penalty". In New Jersey, Mr Forrester's campaign has run attacks by Mr Korzine's ex-wife that he "let her and New Jersey down". The latter has hit back with ads featuring a paralysed 19-year-old in a wheelchair criticising Mr Forrester's opposition to stem cell research.
But tomorrow, all that matters are the results - and in that sense, for Mr Bush to hit the campaign trail in person, at a moment when he has never been more unpopular, is a calculated risk that could backfire badly.
A year ago, Mr Bush carried traditionally Republican Virginia over his Democratic challenger John Kerry by a convincing 54-45 margin. This time Mr Kaine is claiming that the eleventh-hour appearance of Mr Bush - whose approval ratings have fallen below 40 per cent - could hand him victory.
If so, then the implications would be considerable. To Republicans fighting the 2006 mid-term elections, it would send the message that proximity to this President does not pay. For Democrats, it would be an indirect boost to the White House ambitions of the outgoing Democratic Governor, Mark Warner.
Mr Warner is a moderate and a skilled administrator who has shown he can win in a state of the old Confederacy swept by Mr Bush in both 2000 and 2004 - a perfect CV for the next Democratic presidential nominee.
Barred by Virginia law from seeking a second term, Mr Warner is leaving office with approval ratings of 80 per cent. Mr Kaine, his deputy, has stressed how he would continue the policies of his predecessor.
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