Voting in the US presidential race began yesterday as the first ballots were cast in the state of Virginia, part of an unprecedented nationwide surge in early voting that is forcing Barack Obama and John McCain to recalculate their campaign strategies.

With more than six weeks before election day, Virginia is the first of 36 states to allow early voting this year, with at least a third of the electorate predicted to vote before November 4. It is a record-high number that has forced both candidates to change turnout plans, travelling schedules and the timing of advertisements.

Early voting is taking place in a string of key battleground states – including Ohio, Wisconsin, Florida and Minnesota – where Mr Obama and Mr McCain are tied, and where a few thousand votes could decide the outcome in each state.

The large number of states allowing early voting has rendered traditional campaign strategies obsolete. No sooner had Mr Obama and Mr McCain picked running-mates and held their conventions than they had to turn their attention to “closing messages” in many states at a time when they would usually have just begun stumping. Only 11 states permitted the practice in 2000 – part of a strategy to increase voter turnout. Democrats have pushed for it because they believe that it reduces the disenfranchisement of poor and black voters.

Iowa, a key swing state, starts early voting on Tuesday, less than three weeks after the end of the Republican convention. Ohio – allowing early ballots for the first time – opens on September 30, with Florida opening certain polling stations on October 20.

“We could have 40 million people voting before November 4,” said Tad Devine, a Democratic strategist. “The candidates are changing their schedules and changing their media buys. It is having an unprecedented impact.”

Meanwhile, the turmoil on Wall Street and the government rescue package for the US financial markets announced by President Bush yesterday – expected to cost hundreds of billions of dollars – continued to dominate the campaign. Polls this week suggest that the crisis has shifted the momentum slightly back in Mr Obama’s favour. Yet a big survey of ten battleground states showed the reality of the race: it is too close to call.

In another development, Todd Palin, the husband of John McCain’s running-mate, refused to testify in an Alaskan investigation into whether his wife abused her powers by dismissing her police chief to settle a score.

Mr McCain and Mr Obama gave speeches fleshing out how they would solve the financial crisis if elected.

Speaking in Wisconsin, Mr McCain said that the US Federal Reserve should stop bailing out failed financial institutions. He again railed against the greed of Wall Street, and criticised Mr Obama for his links to Freddie Mac and Fannie Mae, the mortgage giants bailed out by the Government.

Mr Obama took large campaign donations from both companies and the former head of his vice-presidential vetting team, Jim Johnson, is the former head of Fannie Mae. “While Fannie and Freddie were working to keep Congress away from their house of cards, Senator Obama was taking their money,” Mr McCain said.

Mr Obama largely refrained from attacking Mr McCain, and instead asked him to work with him on legislation to help middle-class families. Yet his campaign released its own advert criticising Mr McCain’s “fundamentally wrong” economic advisers – a reference to his opponent’s blunder on Monday that “the fundamentals of our economy are strong”.

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