WASHINGTON – Republicans continued Tuesday to block Senate efforts to begin formal debate on the most sweeping overhaul of the nation’s financial regulatory system since the Great Depression, as political sniping turned uglier and more partisan.

Democratic leaders were happy to cast Republicans as allies of Wall Street because of their obstruction of the measure, while Republicans insisted that they were delaying the bill to ensure that taxpayers won’t have to finance any more bailouts. Both sides were posturing with an eye on November’s congressional elections.

Still, at the same time, Senate negotiators continued cordial private talks aimed at reaching a bipartisan deal.

“We have made considerable progress in the last several days,” said Sen. Richard Shelby of Alabama, the top Republican on the Senate Banking Committee. He and Banking Committee Chairman Christopher Dodd, D-Conn., have continued private talks.

Publicly, Democrats spent a second day futilely trying to crack Republican solidarity in opposition to beginning formal debate on the bill, written largely by Democrats.

In a replay of Monday, the 57-41 vote fell three votes short of allowing the Senate to proceed to formal debate, a process which would include considering amendments.

“I do not understand the strategy of forcing these divisive votes,” said Sen. Susan Collins, R-Maine, a moderate whose support probably will be needed for a bipartisan majority.

“It’s very strange to hear both sides say important negotiations are continuing, and then keep taking these votes.”

When she was asked whether the drumbeat of votes could erode bipartisan cooperation, she said, “It doesn’t help it.”