Obama said the upheaval was "the most serious financial crisis since the Great Depression" and blamed it on policies that he said McCain supports.
"This country cannot afford four more years of this failed philsophy," Obama told a cheering outdoor rally in western Colorado.
Meanwhile, McCain said in a statement that the Wall Street turmoil underscores the need to overhaul "the outdated and ineffective patchwork quilt of regulatory oversight in Washington." ()
"It is essential for us to make sure that the U.S. remains the pre-eminent financial market of the world. This will be a highest priority of my administration. In order to do this, major reform must be made in Washington and on Wall Street," McCain said in his statement.
He added: "The McCain-Palin administration will replace the outdated and ineffective patchwork quilt of regulatory oversight in Washington and bring transparency and accountability to Wall Street. We will rebuild confidence in our markets and restore our leadership in the financial world."
Later, at a rally in Jacksonville, Fla., McCain said he still believes the fundamentals of the nation's economy are strong. "Our economy, I believe, still, the fundamentals of our economy are strong, but these are very very difficult times, so I promise you: We will never put America in this position again. We will clean up Wall Street," McCain said.
Obama's statement, issued as he prepared to fly to Colorado to begin a swing through contested Western states, was intended to serve two purposes: to link McCain with the unpopular presidency of George W. Bush and to express sympathy with the anxiety of most Americans who say the economy is issue No. 1 in the election.
"The challenges facing our financial system today are more evidence that too many folks in Washington and on Wall Street weren't minding the store," Obama said in a statement. "Eight years of policies that have shredded consumer protections, loosened oversight and regulation, and encouraged outsized bonuses to CEOs while ignoring middle-class Americans have brought us to the most serious financial crisis since the Great Depression."
"I certainly don't fault Sen. McCain for these problems," Obama said, "but I do fault the economic philosophy he subscribes to."
Over the weekend, advisers both to McCain and Obama said they did not favor a government bailout of Lehman Brothers like that previously provided to Fannie Mae and Freddie Mac. The government also help engineer the recent sale of Bear Stearns Cos. to J.P. Morgan & Co.
"I am glad to see that the Federal Reserve and the Treasury Department have said no to using taxpayer money to bailout Lehman Brothers, a position I have spoken about throughout this campaign," said McCain. "We are carefully monitoring the financial markets, including the duress at Lehman Brothers that is the latest reminder of ineffective regulation and management. Efforts must also be focused on ensuring that the deposits of hardworking Americans are protected."
During his speech, McCain reiterated that position, saying, "We believe that time has come and gone that taxpayers should be viewed as the solution to problems not of their making."
McCain also underscored his message with a new campaign television commercial titled, "Crisis."
It said, "Our economy in crisis. Only proven reformers John McCain and Sarah Palin can fix it. Tougher rules on Wall Street to protect your life savings. No special interest giveaways. Lower taxes to create new jobs. Offshore drilling to reduce gas prices."
At the rally in Colorado, Obama attacked McCain for the ad which promises "change that we need."
"Sound familiar?" said Obama, who has made change the central theme of his campaign. "Let me tell you, instead of borrowing my lines he needs to borrow some of my ideas. Change isn't about slogans. It's about substance."