Barack Obama represents inexperience, risk and instability at a time when America needs swift and bold leadership, his presidential rival John McCain said.
"Perhaps never before in history have the American people been asked to risk so much based on so little," Mr McCain said.
The Republican senator also proposed a 52.5 billion dollar (£30.1bn) economic plan that would eliminate taxes on unemployment benefits and cut the capital gains tax.
He was speaking to voters in the battleground state of Pennsylvania just three weeks before election day as he prepares to go head-to-head with Mr Obama in the third and final presidential debate on Wednesday night.
Mr McCain trails his Democratic rival nationally by more than seven points, according to the average of polls by RealClearPolitics.com, and his campaign aides have said they want to change the subject from the economy as they try to get their presidential bid back on track.
The two men will meet at Hofstra University in New York state for the final debate after Mr Obama was widely seen to be the "winner" of their first two encounters.
On Monday, Mr McCain raised expectations of his own performance as he pledged to "whip his you-know-what".
Mr McCain said Mr Obama's plan for the economy was "an invitation to capital flight, and therefore to continued instability in the market, at a moment when exactly the opposite is needed".
"He is an eloquent speaker, but even he can't turn a record of supporting higher taxes into a credible promise to cut taxes," Mr McCain said.
"What he promises today is the opposite of what he has done his entire career.
"You can look at the record of what he's done or you can just go with your gut, but either way you're left with the same conclusion: Senator Obama is going to raise your taxes.
"And in this economy, raising taxes is the surest way to turn a recession into a depression."
