Returning to the scene of a broken political promise, Democrat Bill Bradley and Republican John McCain today called a temporary truce in partisan politicking and signed a pledge to turn down huge sums from their parties if either of them becomes the presidential nominee.

Bradley, a former Democratic senator from New Jersey, said he and McCain, a Republican senator from Arizona, were "competitors who disagree on many issues," but were "willing to join together for a higher purpose: to put an end to the plague of money in our national politics." They promised, if they won their party's nomination, to reject "soft money" spending by the party to boost their presidential campaigns.

The two, wearing overcoats and gloves to ward off the morning frost in the yard of a senior citizens' center here, stood before a granite bench marking the scene of a past moment of bipartisan bonhomie. In a 1995 debate at the senior center, President Clinton and Newt Gingrich (R-Ga.), then the House speaker, spontaneously shook hands on an agreement to work to limit campaign funding, then quickly shelved it.

Coming together for the event just six weeks before the New Hampshire primary on Feb. 1, Bradley and McCain are gambling that the prospect of change in the nation's campaign finance system will excite the independent voters of New Hampshire, who make up 37 percent of the electorate and can vote in either primary.

In unusual tag-team attacks, Bradley and McCain each used the opportunity to criticize the front-runner in the other party. Bradley said, "I personally think that the governor of Texas will demonstrate that you can raise too much money in politics--that you can have too much money."

And in warm-up remarks to the senior citizens, McCain went right for Vice President Gore. "The scandal of the last few years was not Monica Lewinsky--the scandal was the debasement of every institution of government by the Clinton-Gore campaign."

Referring to Gore's statement in the wake of reports that he had solicited contributions from his White House office, McCain said, "The vice president of the United States said there is no controlling legal authority. When I'm president, there will be a controlling legal authority."

The promise that both men signed reads, "We pledge that as nominees for the Office of President of the United States we will not allow our political parties to spend soft money for our presidential campaigns, and we commit to working together toward genuine campaign finance reform."

"Soft money" refers to the unlimited contributions that individuals, corporations, and labor unions can give to political parties.

Although such funds are not supposed to be spent directly to influence federal elections, in reality soft money has become an important part of presidential campaigning, used to finance advertising that boosts the party's nominee--or attacks the other side--as well as for voter turnout efforts.

Since first announcing his soft-money challenge in July, Bradley had said his pledge would be operative only if his Republican opponent agreed. Ted Koppel of ABC News, who moderated the candidates' town hall meeting for broadcast on tonight's "Nightline" program, asked Bradley how that did not "undermine the high moral tone of your stance."

Bradley then modified his position, saying he has not ruled out refusing soft money even if the Republican nominee accepts it, and would decide at the time. But he said he confronts different circumstances than McCain, since he could face Texas Gov. George W. Bush and his record war chest.

Bush has cited union spending on behalf of Democratic candidates in opposing the notion of giving up soft money spending in the presidential campaign. "We cannot afford a version of campaign finance reform that unilaterally disarms our Republican Party and our conservative principles," he said in a statement today.

Not wanting to be left out of the festivities, Gore, the only other Democratic candidate, took a full-page ad in this afternoon's Claremont Eagle Times promising to put campaign finance reform "at the top of my agenda" if elected and promised, if he is the nominee, to "ban soft money, providing the Republican also agrees--a position I endorsed two and a half years ago."

Bradley retorted, "Well, I'm glad he's finally come over."

Gore, in a conference call with reporters in New Hampshire and Iowa, said he--not Bradley--had a long record of supporting changes in the campaign finance laws. "It is a fact that he served in the Senate more than 6,000 days before he ever put his name on a campaign finance reform proposal," Gore said.

Bradley, who had not previously mentioned campaign finance reform in his advertising, today began broadcasting commercials in Iowa and New Hampshire that show him telling a woman she needs "a president who's going to put this right up there close to the top of the agenda."

McCain acknowledged "great reason for skepticism" about today's promise, but said he was committed to "the last breath I draw" to removing "one of the most pernicious aspects of a presidential campaign."

New Washington Post-ABC News polls indicate that New Hampshire voters have more faith in McCain than in any of the other leading presidential candidates to handle campaign finance reform, but his reputation as a reform hawk has not yet spread nationwide.

Asked which of the four leading presidential candidates they trusted most to handle the issue of campaign finance reform, 43 percent of likely New Hampshire primary voters chose McCain. Less than half as many (20 percent) chose Bradley.

Democracy 21, a nonpartisan group in Washington, estimates that a record $550 million will be spent on this year's presidential race, up from $465 million four years ago. The political parties spent $272 million in soft money on all races last year, and several authorities in the field said that could double this year.

Larry Makinson, executive director of the Center for Responsive Politics, said that although today's meeting was obviously at least partly a publicity stunt, the promise could be "a seismic event in presidential politics."

Makinson said that if Bradley became the nominee and were willing to take the pledge unilaterally, the election "would become a referendum on who's paying for politics in this country." But he said party leaders likely would steer contributions to other interest groups that could buy ads to benefit the party while technically complying with the promise to give up soft money.

At the town hall meeting, Roger Stenson, the executive director of Citizens for Life, an affiliate of the antiabortion National Right to Life Committee, voiced the complaint of many conservative groups that a ban on soft money could limit their ability to get their message out.

McCain shot back, "If money is free speech, sir, the big interests are sitting in front with a megaphone."

Staff writer Ceci Connolly, with Gore in New Hampshire, and assistant polling director Claudia Deane in Washington contributed to this report.