Vincent R. Reinhart, a former Federal Reserve economist now at the conservative-leaning American Enterprise Institute here, said that, in retrospect, “it would have helped for the Bush administration to empower the folks at Treasury and the Federal Reserve and the comptroller of the currency and the F.D.I.C.”  the Federal Deposit Insurance Corporation  “to look at these issues more closely.”

He said it would also have helped “for Congress to have held hearings.”

Instead, voices inside the administration for tougher policing of Wall Street found themselves with few supporters. William H. Donaldson, a former Wall Street executive with respected Republican credentials who became chairman of the Securities and Exchange Commission under Mr. Bush, quit after facing resistance from the White House and Republican members of the agency, who criticized his support for stiffer regulations on mutual funds and hedge funds.

Today, even some sympathetic to Mr. Bush say he cannot disentangle himself from a home-lending industry that ran amok or a banking industry that mortgaged its future on toxic loans.

“The crisis definitely happened on their watch,” said Kenneth S. Rogoff, a professor of economics at Harvard who advises Mr. McCain. “This is eight years into the Bush administration. There was a lot of time to deal with it.”

To some extent, Mr. Bush was simply following a deregulatory pattern set by his predecessor, President Clinton. Perhaps the most significant recent deregulation of the banking industry  the landmark act that allowed commercial banks to expand into other financial activities, like investment banking and insurance  was signed into law by Mr. Clinton in 1999.

Mr. Bush also inherited a culture of borrowing and a frothy housing market that has become “deeply embedded in the American psyche,” Mr. Rogoff said.

And Mr. Reinhart said the markets seemed to be doing so well that few analysts, either in government or the private sector, had a critical eye. “When everybody is doing better,” he said, “it is difficult to see the underlying weaknesses.”