Washington: The US presidential campaign has turned even nastier, with candidates John McCain and Barack Obama blaming each other for the deepening US financial crisis and Congress' failure to pass a $700 billion bailout plan.

Democrat Obama said Monday that his Republican opponent McCain had been opposing needed financial regulation for years. McCain declared that Obama was putting his political ambitions ahead of the good of the nation, saying the race comes down to a simple question: "Country first or Obama first?"

The vote in the the House of Representatives to reject an unprecedented bailout measure only fueled what has become an increasingly bitter race between McCain, a 26-year veteran of Congress and Vietnam prisoner of war, and Obama, a first-term Illinois senator who is seeking to make history as America's first black president.

More than two-thirds of Republicans - President George W. Bush's own party - and 40 per cent of Democrats opposed the bill.

Failed vote

The House vote sent the Dow Jones Industrial Average into a 777-point tailspin - its biggest point drop ever. McCain's chief economic adviser blamed Democrats for the failed vote.

"This bill failed because Barack Obama and the Democrats put politics ahead of country," senior policy adviser Doug Holtz-Eakin said McCain later added his own dig, accusing Obama and his allies of injecting "unnecessary partisanship" into the effort to steady the economy.