Republicans said they were intent on winning substantive changes to the bill and accused the Democrats of rushing the most far-reaching overhaul of the financial regulatory system since the Great Depression. Both sides say they expect the overhaul eventually will be approved.

Democrats charged that Republicans were leaving the country at risk of another financial calamity and siding with wealthy corporate interests. The chief executive of one such firm, Goldman Sachs, the Wall Street powerhouse accused of fraud by federal regulators, is to testify Tuesday before a Senate committee.

Sensing political momentum at a time of deep public anger at Wall Street, Democratic leaders said they would keep the regulatory bill on the floor — and delay the rest of their busy legislative agenda — to ratchet up the pressure on the Republicans.

Democrats said they believed the fight over financial regulation — and signs of economic recovery in many parts of the country — could help turn the tide of anti-incumbent sentiment that has them bracing for substantial losses in November.

President Obama joined in criticizing Republicans for refusing to begin debate, and urged them to “put the interests of the country ahead of party.”

“We are as vulnerable as we are today in the waning days of April 2010 as we were in the fall of 2008,” said Senator Christopher J. Dodd, Democrat of Connecticut and chairman of the banking committee, who is the primary sponsor of the bill. “Nothing has changed, except, of course, jobs have been lost, homes have gone into foreclosure, retirement incomes have evaporated, housing values have declined.”

Republicans, too, see major advantage in their stance, with the Senate minority leader, Mitch McConnell of Kentucky, using the issue to bolster his overarching political argument this year: that the Democrats’ one-party rule in Washington is detrimental.

Mr. McConnell, in a floor speech on Monday, rattled off a list of major legislation that he said had not benefited Americans in the ways Democrats had promised, including the economic stimulus measures and the health care legislation. “The days of taking the Democrats’ word for it are over,” he said.

The vote on Monday was 57 to 41, as Democrats fell short of the 60 votes needed to cut off a filibuster of a motion to proceed.

One Democrat, Senator Ben Nelson of Nebraska, sided with Republicans, apparently out of concern over a provision related to tightening the rules on derivatives trading that was of particular concern to Berkshire Hathaway, the investment company controlled by Warren E. Buffett and based in Omaha.

At the last minute, the Senate majority leader, Harry Reid of Nevada, switched his vote to side with the Republicans — a strategic maneuver that would allow him to call a repeat vote, which is expected on Tuesday. Two Republicans senators, Christopher S. Bond of Missouri and Robert F. Bennett of Utah, did not vote.

With the exception of Mr. Nelson’s opposition, the result was expected: Republicans had warned for more than a week that they would block floor debate of the legislation.

In the days ahead, the fight in the Senate seems likely to hinge on a question raised forcefully in recent days by Mr. McConnell: Does the legislation still contain loopholes that could allow future taxpayer-financed bailouts of failed financial institutions?

Democrats say the bill is written specifically to prevent such bailouts, and have accused Republicans of blatantly misrepresenting the measure.

But Republicans insist government bailouts are still possible. They pointed to language, for instance, in a chapter on liquidating failed banks that established a “strong presumption” of losses for creditors and shareholders. Some Republicans say those losses should be mandatory.

Senator Judd Gregg, Republican of New Hampshire, said Republicans wanted to prevent a collapse like the one in 2008 but warned that Democrats were in danger of strangling the economy with excessive regulation.

“We shouldn’t put in place a regulatory regime that overly reacts and, as a result, significantly dampens our capacity to have the most vibrant capital and credit markets in the world,” he said.

After meeting briefly on Monday, Mr. Dodd and Senator Richard C. Shelby of Alabama, the senior Republican on the banking committee, reported no progress.

The bill, developed in months of talks between senators in both parties, would touch every aspect of the financial system.

It would authorize the government to shut down a financial institution deemed to pose a threat to stability of the system, using a $50 billion fund financed by big banks to help the failed company meet financial commitments while it is being wound down.

The bill would also establish a consumer protection agency intended to end predatory lending practices and require that consumers receive detailed information on mortgages, credit cards and other financing. It would provide new oversight of hedge funds and impose tough rules on the trading of derivatives, the financial instruments at the center of the 2008 economic crisis.

It would restructure the federal system of bank regulation, moving many small banks out from under the Federal Reserve, while providing shareholders of public companies with greater say in electing directors and an advisory role on executive pay.

The Republicans said there were numerous problems in the Democrats’ legislation — from the omission of provisions dealing with the mortgage giants, Fannie Mae and Freddie Mac, to disputes over the specific language. They said the bill would give too much power to the new consumer protection bureau.

Republican aides on the banking committee said they were working to finalize their own version of a financial regulatory bill, but they said it was unclear when, or if, they would release it.

Mr. Nelson last week supported the new derivatives rules as a member of the Agriculture Committee, which shares jurisdiction on derivatives because it oversees the Commodity Futures Trading Commission. That bill would have exempted the holders of existing derivatives contracts from posting collateral or margin requirements.

But in the deal reached over the weekend among Democrats, that provision was removed, angering Mr. Nelson, Congressional aides said.

April 26, 2010