Rebounding from its recent failure to unseat Sen. Arlen Specter (R-Pa.), the conservative Club for Growth is planning to throw its weight -- and money -- into two dozen more congressional races this year, including at least four GOP primaries for the Senate.

In Senate races, the club plans to weigh in on internal GOP struggles in Oklahoma, South Carolina, Florida and Georgia, where the choice of a senatorial nominee could help determine whether Republicans retain control of the closely divided Senate, according to a club official.

It also plans to get involved in about 20 House contests. The club scored a qualified victory Tuesday in a GOP primary for a House seat in Nebraska, where the establishment-backed candidate it had targeted for defeat lost in a seven-way race. But the club-supported candidate was also defeated.

Analysts disagree over whether the anti-tax group gained or lost clout as a result of its close but losing effort on behalf of Rep. Pat Toomey (R-Pa.), Specter's conservative challenger. But many say the club is well positioned to continue as an influential player in GOP politics.

"I think moderates will know it's an organization with substantial resources and know they will have some vulnerability in primaries," said the American Enterprise Institute's Norman J. Ornstein. The club's goal is to be a "gravitational force pulling a lot of Republicans to the right" and "just giving Specter a major scare and headache was enough," Ornstein added.

Specter, a 24-year Senate veteran and dean of its GOP moderates, was the club's prime target for this year, offering a high-profile opportunity to strike a blow for the club's goal of lower taxes, less spending and smaller government. The club provided some early legitimacy for Toomey's campaign and ultimately spent at least $2.3 million on it, an unusually high figure for an outside group in a Senate primary. With an assist from President Bush and other GOP leaders, Specter eked out a 13,000-vote margin of victory in the April 27 primary.

The outcome was "a short-term defeat but a long-term building block for the Club for Growth," its president, Stephen Moore, said in an interview. "We certainly live to fight another day."

"I hope it discourages them, but I don't think it will," said Rep. Amo Houghton (R-N.Y.), a leading House moderate and critic of the club, who is retiring this year. "At some point, I guess they'll just fall off the flat face of the earth."

Rather than bolstering the club, the Pennsylvania vote should encourage moderates, Specter said. "It shows moderates that the Club for Growth can be beaten," even when it goes all-out against one of them, he said. But the party has to be prepared to rally behind its moderates, Specter added.

For Senate and House races this year, the club has raised about $8 million, as much as it raised in all 2002. Moore said the total for this year is expected to be $12 million to $15 million.

In GOP primaries over the next few months, Moore said, the club plans to back Rep. Jim DeMint in South Carolina, former House member Tom Coburn in Oklahoma, state House Speaker Johnnie Byrd in Florida and former Godfather's Pizza Inc. chairman Herman Cain in Georgia. All are conservatives and some are bucking candidates supported by the GOP establishment, such as former Oklahoma City mayor Kirk Humphreys in Oklahoma and former governor David M. Beasley in South Carolina.

Moore said the club also intends to support several other candidates in the fall, including Illinois Republican Jack Ryan, whom it backed earlier in a nine-way GOP Senate primary.

The club has yet to designate all its favorites in House races but plans to get involved in both primary and general election contests, Moore said. In the 1st District race in Nebraska, it spent nearly $170,000 on radio and television ads to defeat Curt Bromm because of his votes as a state legislator for tax increases to balance the budget. Bromm came in second behind former Lincoln City Council member Jeff Fortenberry. Greg Ruehle, the club-supported candidate, came in third. The seat is held by 13-term Rep. Doug Bereuter, who is retiring.

The club is considering supporting a challenge by Cayuga County legislator David L. Walrath to moderate Rep. Sherwood L. Boehlert (R-N.Y.) in the September New York primary. With modest help from the club, Walrath lost to Boehlert by about 3,000 votes in the primary two years ago.

Even though the group has ambitious plans for the rest of this year and for future elections, it also faces obstacles.

The club, formed five years ago, has yet to demonstrate it can defeat an incumbent lawmaker who defies its orthodoxy on taxes and other issues -- the kind of ultimate sanction that might scare moderates into voting more conservatively than they are now.

It has supported many winning candidates but came close to defeating Republican incumbents only twice, former representative Margaret S. Roukema (N.J.) in 2000 and Specter this year. Roukema retired in 2002 and was succeeded by Scott Garrett, the conservative she narrowly defeated two years earlier.

Moore contends that the threat of opposition from the club helped persuade Specter and Sen. George V. Voinovich (R-Ohio) to vote for Bush's 2003 tax cut -- a claim disputed by the two senators. Voinovich has said he voted for the tax reduction only after it was pared down to the amount he supported in a close budget vote earlier in the year.

Sarah Chamberlain Resnick, executive director of the moderate Republican Main Street Partnership, which fought the Club for Growth in Pennsylvania, took issue with Moore's claim that moderates are heeding the club's threats. "Moderates represent their districts," not outside groups, she said. The club "isn't winning, so it's not shaking anyone up."

Voinovich agreed. "If they know anything about me, they know I just get more ornery" when pressured, he said. As for the club, "I just ignore them," he added.

Perhaps more significantly, the club's targets of opportunity are shrinking, in part, ironically, because the number of moderates in both houses was dwindling even before the Club for Growth got in the act. Moderates can be critical on close votes, especially in the narrowly divided Senate. But many are retiring and are often succeeded by conservatives.

Sen. Arlen Specter, left, narrowly defeated challenger Rep. Pat Toomey, backed by the Club for Growth, in the Pennsylvania Republican primary.