Senate Republicans say they fear they might have lost their edge on the energy issue after some of their GOP colleagues joined the “Gang of 10” that is pursuing a bipartisan compromise.

Formed over the summer, the group has attracted increasing support, with its ranks swelling to 16 members, and Majority Leader Harry Reid (D-Nev.) has agreed to give their proposal a floor vote next week.

After weeks of working relatively unmolested, Republican members of the gang found themselves a target of party criticism this week.

According to lawmakers attending the weekly Conference luncheon Tuesday and the Republican Steering Committee’s Wednesday lunch, Members panned the policy provisions as well as the compromise’s potential to cripple the party’s sole advantage in an otherwise brutal campaign cycle.

Sen. Saxby Chambliss (Ga.) pitched the deal at the GOP gathering. One Republican Senator called the confrontation between group members and opponents at the Tuesday lunch “very one-sided.”

“Saxby got up and made a presentation, and he got dumped on by a whole bunch of people,” the lawmaker said.

Republicans say they have had success blaming Democrats for high gas prices and for their refusal to allow offshore drilling.

“From a political standpoint, I think it does sort of muddy the message,” Republican Conference Vice Chairman John Cornyn (Texas) said.

Cornyn acknowledged that the Gang of 10’s deal could also help the lone Senate Democratic incumbent seen as vulnerable, Sen. Mary Landrieu (La.).

Some of the GOP concerns have been focused on policy issues. Gulf-state lawmakers released a letter Wednesday to members of the group asking them to make changes to their bill. The letter was signed by Cornyn, Sen. Kay Bailey Hutchison (Texas), Alabama Sens. Richard Shelby and Jeff Sessions, and Sens. Thad Cochran (Miss.), Roger Wicker (Miss.) and David Vitter (La).

In the letter, the Republicans urged their colleagues to drop a tax provision they say “singles out production in the Gulf [and] is not only arbitrary, but it will discourage production where some of the largest discoveries of oil and gas are known to exist.”

Cornyn and others also acknowledged that much of the unhappiness with the group’s members stems from the fact that it could undercut the GOP’s energy messaging efforts. Faced with few winning polling issues, Republicans seized on the energy issue and gas prices in particular this summer.

They appear to have some success, and Republicans said the Gang of 10’s bill will at best confuse that message and at worst give Democrats cover just weeks before the November election.

Sen. John Thune (R-S.D.), one of the original members of the group, acknowledged that the party is split over the approach. “There’s no question it’s stirred up a debate,” Thune said.

But he rejected complaints about the political implications of the deal, arguing that a bipartisan deal, even if it does not succeed, is still good for Republicans.

“We think it’s good politics for us to do something,” he said, noting that two vulnerable Republican incumbents — Sens. John Sununu (N.H.) and Norm Coleman (Minn) — have joined. “People who are saying it’s bad politics are blunted by the fact the people who are joining up are in tough races,” he said.

Under Reid’s schedule for next week, the chamber will first vote on a Democratic energy bill that is widely expected to fail. Reid has said he would then like to vote on the group’s proposal, and leadership aides have said Reid has made it clear to his Members that he does not want his party to take any blame for the bipartisan agreement failing. Reid has said he would then like to have a vote on a Republican version, which is also expected to fail.

With much of the Democratic caucus likely to vote for the bipartisan deal, Democrats have acknowledged Reid is aiming to corner Republicans into either voting for the bill — and thus limiting the impact of their energy attacks — or scuttling it themselves.

“If we’re not going to do something that’s good for the country, then let’s not do anything that hurts our candidates,” said National Republican Senatorial Committee Chairman John Ensign (Nev.).

A senior GOP aide said Republican lawmakers are particularly upset with the Gang of 10 members because their deal has little chance of being signed into law. Although Democrats appear willing to back the bipartisan agreement in hope of blunting the GOP’s energy attacks, it is not clear that enough Republicans will vote for it to over-come an expected filibuster. Even if it passes, House Republicans and the White House oppose the package. Republicans said there is no chance President Bush would sign it.

Given that scenario, Republicans said, many in their ranks are struggling to see the political upside to pursuing the proposal.

“Even if you accept Saxby’s argument that the gang bill is the only thing to get to 60 and that we should do it ‘to get something done,’ the House may not pass it — and worse, the president will veto it. So why are they going out of their way to hurt our message? Instead of ‘drill here, drill now,’ the gang bill is ‘tax here, tax now,’” one frustrated Republican said.

Another Republican, speaking on condition of anonymity, was more blunt: “It has the political acumen of the Dubai Ports deal. You’d have to work really hard to come up with a worse idea.”

Following a meeting of the group Wednesday afternoon, Sen. Kent Conrad (D-N.D.) acknowledged that there are opponents of its approach on both sides of the energy debate but said the members remain committed to moving a bipartisan bill.

“There are groups and people on both sides who don’t wish us well, and they’re working overtime. Our group is holding firm,” Conrad said.

Emily Pierce contributed to this report.