The Senate scrambled frantically early last night to salvage major crime legislation after failing for a second time to end delaying tactics that threatened to kill the measure.

After hours of squabbling over who was to blame for imperiling the legislation, which would authorize the death penalty for 30 federal crimes and impose a partial ban on assault weapons, Democrats and Republicans began trading proposals for resolving remaining disputes and speeding passage of the measure.

Senate Judiciary Committee Chairman Joseph R. Biden Jr. (D-Del.) said last night he thinks chances of getting a bill are now "better than 50-50," but it may take until early next week to work out an agreement for voting on it.

The failure to halt the delaying tactics followed an intense lobbying effort against the assault weapons curbs in the bill by the National Rifle Association, which sent out blistering letters to its members attacking senators who broke ranks with the gun lobby to help the provision carry by a one-vote margin last month.

Despite Democratic leaders' predictions that they would succeed in their second try at curtailing the delaying tactics, the Senate fell three votes short of the 60 needed to impose cloture, which would have limited debate and weeded out many of the 330 proposed amendments that have bogged down the bill.

The vote was 57 to 37, with 46 of 53 Democrats supporting cloture and 30 of 41 Republicans opposing it. Thirty-two of the 37 votes against cloture came from senators who had opposed the assault weapons constraints. At least two others came from senators who oppose capital punishment. Many senators also complained that cloture amounted to imposing a "gag rule" that would preclude consideration of their own pet anti-crime projects.

Senate Majority Leader George J. Mitchell (D-Maine) had warned that the bill would be shelved if the second cloture attempt failed, and, shortly after the vote was announced, Biden said grimly that the bill had "just died."

With Democrats clearly poised to blame the Republicans for scuttling the crime bill, including the major expansion of death penalty provisions in federal law, GOP leaders scrambled to bring the measure back to life and blamed the Democrats for jeopardizing it.

"Why give up after two tries. . . . If the majority wants a crime bill, it's within their grasp," said Minority Leader Robert J. Dole (R-Kan.).

But an angry Mitchell noted that he had assurances of 60 votes on Tuesday, when cloture failed, 54 to 37, on the first try. What the Senate faces is an "endless game of pick-up-sticks" on the issue, always just short of the magic number, he contended.

Then Mitchell got to the politics of the issue. "Let's not have any misunderstanding where the responsibility lies for not getting a crime bill," he said. "It's not the majority leader who's taking the bill down but senators who voted against cloture who are taking the bill down."

Sen. Alan J. Dixon (D-Ill.) was even more pointed. Republicans "go out and beat us to death about crime . . . they bring out Willie Horton {the furloughed Massachusetts convict made famous in the 1988 presidential campaign}. . . . Then when they get an opportunity to vote against crime, for some reason they don't do it," he said.

After a brief huddle off the floor, Biden and Sen. Strom Thurmond (R-S.C.), ranking Republican on the Judiciary Committee, returned to suggest a compromise, drafted by Thurmond, that would confine votes to key issues in the bill that have not yet been addressed. Mitchell went along with the proposal, but Republicans, caucusing into the evening, made a counteroffer to slash the list of amendments to 12 by each side and submitted the plan for consideration by Democratic leaders. If the Democrats go along, both sides will try to pare their amendments to 12 or fewer. However, Biden is also insisting that Republicans agree to forgo more votes on these issues for the rest of the year.

The bill would reinstate and expand death penalty provisions for 30 offenses, primarily involving murder, espionage and treason, and limit the number and duration of appeals by prisoners on death row. It would also ban manufacture and sale of nine kinds of semiautomatic assault weapons most often used in violent crimes. A provision that would permit use of illegally seized evidence in trials under some circumstances would be dropped under a tentative agreement between Biden and the Republicans.

Most of the provisions reflect President Bush's key anti-crime proposals to Congress, although the assault-weapons provision goes substantially beyond import curbs he ordered last year by restricting domestic as well as foreign weapons.

A letter sent to Virginia NRA members accused Virginia Sens. John W. Warner (R) and Charles S. Robb (D) of a "double cross" and "breaking their campaign pledge that they would fight crime by targeting criminals not firearms." The vote to curb assault weapons "sets America on the road to universal gun confiscation," the letter said. Both Warner and Robb voted for the curbs and for cloture both times, as did Maryland Sens. Paul S. Sarbanes (D) and Barbara Mikulski (D).