Two years ago, New Jersey Sen. Robert Torricelli raised $100 million to help Democrats in their drive to win control of the Senate. Now, he's giving up his own tattered re-election campaign before he becomes the reason they lose it.

But preventing the loss of his seat to Republicans will be a challenge for the famously combative senator, brought down by an ethics controversy, and for his party.

The Republicans are one obstacle. The election calendar is another.

Even before Torricelli announced his withdrawal Monday at a news conference in Trenton, N.J., GOP officials said they were ready to go to court to block Democrats from fielding a replacement candidate so close to the election.

"The laws of the state of New Jersey do not contain a 'we think we're going to lose so we get to pick someone new' clause," taunted Torricelli's challenger, Doug Forrester.

On a practical level, Democratic party officials have yet to settle on a consensus choice to take Torricelli's place on the ballot. Even assuming an agreement by Tuesday on Rep. Bob Menendez or another replacement, they will have only five weeks to shed the ill-effects of Torricelli's ethics woes, introduce their candidate to the voters around the state and rough up Forrester on the issues.

"Any Democratic candidate is going to walk into an essentially turnkey operation," said Jim Jordan, executive director of the Democratic campaign committee, referring to the campaign organization that Torricelli and the party has in place.

Among those assets will be the benefits of the research that Torricelli's campaign did on Forrester, and the millions of dollars in television advertising that the party reserved for Torricelli.

And yet, the man that many party leaders would like to see on the ballot, former Sen. Bill Bradley, did not immediately return a phone call during the day from Senate Majority Leader Tom Daschle. One former senator who did express interest, Frank Lautenberg, is 78 and last ran for office eight years ago.

Other possible replacements, Reps. Menendez, Rob Andrews and Frank Pallone, are members of the House, and relatively little known outside their own districts.

Some Democrats said during the day that the party could short-circuit a legal challenge if Torricelli resigned his seat. Democratic Gov. Jim McGrevey would appoint a successor, who would automatically qualify for the ballot, according to these officials, who spoke on condition of anonymity. The subject did not come up at Torricelli's news conference.

The Democrats are defending a one-seat advantage in the Senate in mid-term elections, and the loss of New Jersey would greatly complicate their efforts to retain control.

Until recently, Torricelli appeared to face little difficulty in his bid for a new term in a state that last elected a Republican to the Senate three decades ago.

But that was before the Senate ethics committee severely admonished him, finding that he accepted and failed to disclose gifts from David Chang. Chang is serving an 18-month prison sentence for making illegal donations to Torricelli's 1996 campaign.

Federal prosecutors declined to bring charges in the case. But the ethics committee report triggered a sharp slide in Torricelli's poll ratings and, by his own account, made it impossible for him to change the subject to other campaign issues.

"I cannot talk about war and peace or economic opportunity ... I can't be heard," he lamented at his news conference.

Then it got worse.

Torricelli failed last week to block release of a memo that prosecutors sent to the judge in Chang's case. It said Chang had led federal agents to shops where he said he bought the senator antique sculptures, rugs, jewelry and appliances. Prosecutors said Chang's efforts "greatly advanced" the investigation into the senator's actions, although they acknowledged that Chang's "serious credibility problems" would make him useless before a jury.

As late as last week, according to party officials, Torricelli met with party officials to make sure he had financial commitments from Democrats. There was some irony in that. Torricelli was brought into the Senate campaign leadership in his first year in the Senate, in part for his fund-raising prowess. And as chairman of the campaign committee two years ago, he helped the party raise the money that produced a 50-50 tie.

But by the senator's own account, he confided to Daschle last week that he thought his seat was in jeopardy.

A public poll released over the weekend found Torricelli trailing Forrester by 13 percentage points -- and winning the support of only 34 percent of those surveyed. That marked a sharp decline from an earlier poll in June, before the ethics storm broke.

Beyond the public survey, several sources who spoke on condition of anonymity, said a private poll over the weekend was even worse. It showed a 20-point Forrester lead, they said.