Five months after getting trampled by an aggressive Democratic minority on gun control, Senate Republicans have pulled together, adopted tougher tactics and emerged as the strongest single political force on Capitol Hill.

But their success has raised questions, even within their own ranks, about whether they will pay a price at the polls next year for killing or scaling back popular bills and giving the Democrats ammunition for claims that this is a "do-nothing" Congress.

On most high-profile issues that arose over the last few months, from health care to campaign finance and nuclear testing, Senate Republicans have kept the Democrats at bay and succeeded far more than the fractious House Republicans in staking out a position, rallying their troops and winning.

Since Democrats peeled off enough Republican votes in May to prevail on requiring background checks for sales at gun shows, Senate GOP leaders have gone out of their way to foster unity in their ranks, catering to senators who are up for reelection next year and picking fights that are likely to unite rather than divide their own ranks. They have repeatedly moved to block Democrats before they can unload their own agenda onto Republican bills.

Majority Leader Trent Lott (R-Miss.) "needs only to learn a lesson once," said his friend and ally, Sen. Slade Gorton (R-Wash.).

Lott, now in his third year of running the Senate, has become more confrontational with the Democrats, while House Speaker J. Dennis Hastert (R-Ill.), who took office less than a year ago, is still learning the ropes and seems by nature to be more accommodating.

In the process, Senate Republicans have capitalized on their inherent advantages over both House Republicans and the Senate Democratic minority.

Probably the Senate GOP's biggest advantage is its relatively comfortable margin of control. While the party has only five seats to spare in both houses, its 55 to 45 Senate majority feels bigger than its 222 to 212 House margin. Equally important is the outlook for the 2000 elections: Control of the House is up for grabs, while Republicans appear likely to retain control of the Senate. Senate Republicans feel far less threatened than their House counterparts.

"Panic tends not to yield good political strategy," said John J. Pitney, an expert on congressional Republicans at Claremont McKenna College in California.

There are other factors that make the difference even greater. "In the Senate, there's a notion that the greater good should prevail in order to protect their majority," said Marshall Wittmann, chief Congress watcher at the Heritage Foundation. "There's a certain comity within the Senate Republican caucus that doesn't exist in the House," which is beset by "roving coalitions that have fractured the party" on one issue after another, Wittmann said.

"Over here [in the Senate], we have decided it's better to hang together," said a senior Senate GOP aide. "Over there [in the House], they've decided to hang separately."

In their first big test since their gun fiasco, Senate Republicans three months ago rammed through a slimmed-down version of a Democratic proposal to protect patients in managed-care plans, losing only two of their own votes in the process. By contrast, House Republicans went down to defeat earlier this month on the same issue after 68 of their members defected to support a broader bipartisan bill.

In their latest test, Senate Republican leaders succeeded last week in killing legislation to tighten campaign fund-raising laws by employing rules requiring 60 votes to force action, which enabled them to withstand a number of GOP defections. In the House, under rules calling for a simple majority vote, 54 Republicans defied GOP leaders and joined with Democrats to pass a similar bill by a big margin.

On another major issue, GOP senators held this month in rejecting a nuclear test ban treaty, one of President Clinton's major foreign policy priorities, after Clinton refused to meet their conditions for delaying the vote. The House was not involved because treaties are considered only by the Senate. In this case, it was the Democrats--and the White House--that got trampled.

On the budget, the Senate Republicans' pragmatic approach--fashioning spending bills more acceptable to the administration--appears to be winning the day as Congress nears completion of work on the budget. The Senate GOP has seen comparatively little of the intramural strife that has marked House Republican consideration of the budget.

Each of these developments increased the Senate Republicans' self-confidence and boldness in taking on the Democrats. But whether the Senate GOP's winning streak will continue is anybody's guess. Senate Minority Leader Thomas A. Daschle (D-S.D.) said he expects Democrats to pass a minimum wage increase and predicts that they will eventually prevail on managed health care.

Daschle also argued that Republicans will pay an "incalculable cost" at the polls for actions such as defeat of the Comprehensive Test Ban Treaty and rejection of Missouri jurist Ronnie White, an African American, for a federal judgeship, ostensibly because of his record on the death penalty. "This may work for a while, but ultimately I don't think it can be sustained politically," Daschle said.

Similar concerns have been voiced by some Republicans. "You can only move against the will of people so many times and not suffer the political consequences," said Sen. Olympia J. Snowe (Maine), a moderate who is up for reelection next year. If Congress refuses to act or chooses only minimalist solutions, "there is also a danger of being reduced to political irrelevance," she said. "People will not expect anything of us anymore, and that is dangerous."

Staff writer Eric Pianin contributed to this report.