Washington ? For Sen. Barack Obama, D-Ill., the Wall Street meltdown is a testament to failed Bush administration policies that his Republican rival would continue.

For Sen. John McCain, R-Ariz., the turmoil is the product of cozy relationships and corruption in Washington that can be cleaned up only by “reformers” like him and running mate Gov. Sarah Palin of Alaska.

The two presidential candidates have battled for weeks over which one offers the most dramatic change from the current unpopular administration. On Monday, they seized on the financial chaos to make their cases anew but offered no new proposals.

The McCain campaign quickly released a television advertisement after the disclosure that one financial giant, Lehman Brothers, had filed for bankruptcy and another, Merrill Lynch & Co., Inc., had been bought out.

“Our economy in crisis. Only proven reformers John McCain and Sarah Palin can fix it,” the ad said.

On the campaign trail in Florida, however, McCain sounded a slightly different note when he said the fundamentals of the economy remained “strong.” The Obama campaign immediately pounced on that as evidence that McCain is out of touch with ordinary people.

The growing sense of urgency about instability in the housing and financial sectors may pressure both McCain and Obama to flesh out economic policies that have been vague or overshadowed by a blizzard of character attacks and negative campaigning.

For months, Obama has been calling for increased regulation and accountability for financial institutions. On Monday, he issued a statement that blamed the current administration for the problems and implied again that as president he would push for new regulation of the financial services sector.

McCain signaled some openness to increased regulation of financial institutions to increase transparency of their dealings – though he was more cautious than Obama.

McCain, in a statement, said he would “replace the outdated and ineffective patchwork quilt of regulatory oversight,” but also that a “highest priority” of his administration would be to ensure that the U.S. “remains the pre-eminent financial market of the world.”

Such language is sometimes interpreted as a caution that too much regulation will damage Wall Street’s standing as an economic powerhouse.