Analysts say voters' anxieties about the global financial turmoil is an important factor behind Obama's recent gains.
Sources: ABC News/Washington Post and RealClearPolitics
The results came as McCain and Obama continued campaigning on Monday - just two days before they face each other in their final debate.
"Every day is now crucial on the campaign trail," Al Jazeera's Sebastian Walker said.
"For John McCain, the time is even more precious if he's to overturn his current disadvantage.
"The final presidential debate is in just two days time - whoever emerges victorious there, could hold the key to victory."
In an apparent shift in strategy, the McCain campaign has moved away from what has widely been regarded as a gaffe in taking negative swipes at Obama to chiding the Democrats for celebrating victory too early.
And, struggling to reverse the trend, McCain gave a speech aimed at portraying himself as a fighter who will come back.
"We have 22 days to go. We're six points down. The national media has written us off. Senator Obama is measuring the drapes," McCain said.
"They forgot to let you decide," he told supporters at Virginia Beach, Virginia.
"My friends, we've got them just where we want them!"
Middle class 'rescue'
Obama used his speech in Toledo, Ohio, to hammer home the advantage he is reported to have over McCain on the economy.
"Last week, Senator McCain's campaign announced they were going to 'turn the page' on the economy, so they could spend the last three weeks of the campaign attacking me instead," Obama told supporters.
"His campaign actually said 'if we keep talking about the economy, we're going to lose.'"
|Obama has aimed to reinforce an image as being strong on economic issues [AFP]
At the rally, Obama unveiled what he described as an "economic rescue plan for the middle class".
The proposed steps would cost $60bn over two years and would include temporary tax credits to help create new jobs, penalty-free withdrawals from retirement accounts, a short-term stay on banks foreclosing on homeowners trying to pay off mortgages and greater lending to states and municipalities.
Economic analysts say the proposal is modest compared to the scale of the crisis.
"It is not large enough to serve as a stimulus for the economy," Dean Baker, of the Center for Economic and Policy Research, said.
"Given what I expect to be the severity of the downturn, we're probably going to want to see a lot more spending."
Later on Tuesday, McCain is set to unveil proposals which include tax relief for senior investors affected by severe losses in stock markets.
Doug Holtz-Eakin, McCain’s economic adviser, said McCain will give details of a package worth an estimated $52.5bn.
McCain will propose that seniors pay a maximum tax rate of 10 per cent on money they withdraw from retirement plans in 2009 and 2010, Holtz-Eakin said.
The tax rate will be a reduction from the current tax rate that senior citizens pay; the move would cost an estimated $36bn.
McCain's package also contains a two-year long reduction in capital gains tax on stock profits, worth $10bn, and a two-year-long suspension on taxes paid on unemployment benefit insurance, worth $6.5bn.