One was accused by a fellow Republican of "stabbing us in the back." Another was stiffed by some of his brethren when he held a campaign fund-raiser. And, for a time, their pictures disappeared from the wall where the Senate GOP campaign committee proudly showcases its members.

"It was just a little joke," said Sen. Phil Gramm (Tex.), head of the National Republican Senatorial Committee.

"It was a very trying time," said Sen. James M. Jeffords (R-Vt.).

The cause of the commotion was passage of President Clinton's bill to overhaul congressional campaign financing, which became possible only after Jeffords and a half-dozen other GOP mavericks cut deals with the Democrats and then abandoned their own party's filibuster against the bill.

Now the drama is being playing out again this week as these swing Republicans are playing a decisive role in the fate of Clinton's national service legislation. They favor the principle of national service and hold the key to a compromise that would allow the Senate to pass the bill.

The Republican rebels come from the party's small but strategically important moderate wing, and they include a minister as well as the only senator under federal indictment. And the group rears up every now and then to exert power far beyond its numbers.

They blunted the edges of some of President Ronald Reagan's most conservative initiatives and forced a civil rights bill on a reluctant President George Bush. Now, even though their numbers have shrunk and an increasingly powerful conservative majority within the Senate GOP has purged them from the party leadership, they are demonstrating that they often can provide the margin of victory for either Clinton or the Republicans.

Their weapon is the power of simple arithmetic: It takes 41 votes to sustain a Senate filibuster -- a continuing debate that prevents voting on a bill -- and there are 44 Republicans. Lose more than three Republicans and the GOP loses the most important lever of power it has left in this Democratic-occupied town.

"There's no question that the filibuster and the need to get 60 votes to end it puts enormous power in hands of six to 10 moderates in both parties," said Sen. J. James Exon (Neb.), a Democratic moderate who joined Sen. Dave Durenberger (Minn.), one of the Republican rebels, in drafting the key compromise on campaign finance.

The GOP moderate group varies in size and composition from issue to issue, although members tend to be almost militantly nonideological, more liberal on social issues than they are on fiscal matters, partisan on occasion but more often than not willing to cut a deal.

Most of the time the group includes John C. Danforth (Mo.), an Episcopal priest and a lawyer in private life, as well as Durenberger, accused of hiding ownership of a Minneapolis condominium to collect Senate reimbursement.

Sometimes the moderate wing is just Jeffords, a modest, mild-mannered New Englander who votes more frequently with Democrats than Republicans and drives some conservatives into a sputtering rage with his pleasant but stubbornly independent ways.

It usually also includes a handful of other Republicans who represent states with sizable Democratic constituencies, such as John H. Chafee (R.I.), another amiable but independent Yankee who served in the Senate GOP leadership until he was ousted by conservatives in 1991 for what they described as insufficient party loyalty.

They can be fiercely partisan, as they demonstrated in joining a united GOP front in opposition to Clinton's economic plan, and are deeply immersed in issues, such as health care and environmental protection, that invariably transcend partisan interests.

Sometimes the moderate regulars are augmented by one or more conservatives who are drawn to them because of a particular issue.

The Campaign Finance Seven were a case in point.

In addition to Jeffords, Chafee, and Durenberger, Sen. William S. Cohen (R-Maine), Sen. Nancy Landon Kassebaum (R-Kan.), who delicately balances her loyalty to her senior senator, Minority Leader Robert J. Dole (R-Kan.), and her moderate instincts, frequently joins the rebels, as she did on campaign finance. Sen. John McCain (R-Ariz.), a conservative with maverick instincts, occasionally finds himself in the moderate camp. Sen. Larry Pressler (R-S.D.) wanders in and out of all camps, often inexplicably.

Despite Gramm's "little joke," the rebellion over campaign finance earlier this summer was no laughing matter to leaders of both parties.

Republicans learned that the filibuster, which they used so successfully in killing Clinton's economic stimulus bill in April, was no more than an idle threat if the Democrats could peel off defectors with compromises.

And Democrats learned that there may be a high price to pay for winning over enough Republican votes to break a filibuster. The Republican deal-makers forced the Democrats to drop from the campaign finance bill many of the perceived advantages for Democratic candidates. Even more important, they reserved the right to rejoin a GOP filibuster against a House-Senate compromise later this year, assuring that their weight will continue to be felt.

It was a repeat performance -- on a larger scale -- of an earlier compromise that enabled the Senate to break a Republican filibuster and pass the "motor voter" bill to ease state voter registration rules.

It was also a precursor of opportunities confronting this quintessential political minority -- the minority faction of the minority party -- on issues from health care to welfare reform, national service, environmental protection, abortion and domestic spending priorities.

There is more to the game than just proving that they are not the 90-pound weaklings of the legislative process, the senators contend.

Many of the moderates say they are drawn to some of the change-oriented aspects of Clinton's agenda, including health care and political reform, and are prepared to respond to what they regard as moderate policies from the White House. "To the extent that Clinton comes back toward the center, he'll have the support of this group. To the extent he moves to the left, we'll stay with Dole," Cohen said. "Most of us were elected -- years ago -- to change the way government operates," Durenberger added.

They also say conservative Republicans are paying the price for purging Chafee as head of the Senate Republican Conference, third-ranking post in the party leadership, and insisting on the most conservative choices for other party posts in 1990 and 1992.

While this did not trigger their more independent stance, it was a contributing factor, several of the moderates said. "If you're excluded from the leadership, then you don't feel as beholden to it," Jeffords said.

Another factor is that many of the moderates just don't like the negativism of filibusters. "It isn't very constructive to have Republicans filibustering all the time," Chafee said. "People say you're naysayers and want to know what you are for."

Outside of the fact that most of them come from swing states in the Northeast, Midwest and Pacific Northwest, there are few common denominators linking senators most often found in the moderate camp.

A study earlier this year by Congressional Quarterly showed that the Senate Republicans most likely to vote with Democrats are, in descending order in terms of their votes last year, Jeffords, Arlen Specter (Pa.), Mark O. Hatfield (Ore.), Bob Packwood (Ore.), Durenberger, Chafee and Cohen. Some were consistent, such as Jeffords, who voted more than half the time with the Democrats over the past four years. Others, like Specter, tended to vote more with Democrats in an election year.

Others who often vote with the group are Kassebaum and Danforth, sometimes joined by more conservative mavericks such as McCain and Pressler on campaign finance, Christopher S. Bond (R-Mo.) on family and medical leave legislation, Pete V. Domenici (R-N.M.) on civil rights, or Alfonse M. D'Amato (R-N.Y.) on urban issues. Recently, Democratic legislation to revise the Hatch Act to permit more political activity by federal workers peeled off Republican senators with large numbers of government employees in their states.

There is nothing new about the potential power of centrists in both parties -- the right wing of the Democratic Party and left wing of the GOP -- to provide the margin of victory for either party.

This is especially true in the Senate, where rules, tradition and a relatively narrow Democratic margin of control make every defector a potential deal-maker. In the increasingly more partisan House, moderate Republicans bolt their party less often and less cohesively than they did a decade ago when they were known as "gypsy moths," a liberal counterweight to the conservative Democratic "boll weevils" who supported Reagan's fiscal policies. But even in the Senate, the numbers have to be right, and this -- like the early 1980s -- is one of the times when they are.

With Democrats controlling the Senate 56 to 44 and with Republicans embarked on a filibuster strategy that takes 60 votes to thwart, opportunity has struck again. Even if a few Democrats defect from their party, a half-dozen GOP moderates can make the difference on a cloture vote, enhancing their ability to cut deals with both parties.

Despite the opportunities, however, most of the moderates say they intend to choose their causes with care, both because they agree more often than not with their fellow Republicans and because they do not want to lose all influence with them. As McCain put it, "You walk a fine line between showing your independence and alienating your friends."