Sen. Arlen Specter (R-Pa.), ranking member on the Judiciary panel and a key player in the debate over electronic surveillance, has been drawing barbs from two groups that generally find little in common: the Bush administration and the American Civil Liberties Union (ACLU).

As Congress struggles to overhaul the 1978 Foreign Intelligence Surveillance Act (FISA), the administration and civil libertarians alike are opposing a compromise measure by Specter that addresses one of the thorniest issues in this debate: whether to grant retroactive immunity to the telecommunications firms that took part in the National Security Agency’s warrantless wiretapping program after Sept. 11, 2001.

Many Democrats decried the measure, saying that the immunity provision would let the carriers circumvent the 1978 law and provide no relief to the plaintiffs in the 40-odd pending cases against the companies. Republicans, however, generally favor the Intelligence panel’s bill, and the White House has threatened to veto any legislation that does not grant retroactive immunity — a top priority for the administration. They argue the firms acted in good faith to aid the government after the Sept. 11 attacks.

With a messy and protracted floor debate all but inevitable, Specter and several Democratic allies on the Judiciary panel plan to push an alternative that they hope might clear the 60-vote hurdle: an amendment that would have the government replace the carriers as the defendant. The attorney general or the director of national intelligence would have to certify that the carrier got an authorized request from the government, and the FISA court would then rule whether that request was lawful or reasonable. The government would not be allowed to invoke certain defenses — such as the “state secrets” doctrine — unavailable to private parties.

“The telephone companies … or the defendants in these cases are highly unlikely to pay damages,” said Specter in a December floor speech. “But I believe it is very important that the courts not be foreclosed from making a judicial determination on the issues which are involved.”

Otherwise, retroactive immunity would let the government off the hook for having conducted the program in secret and not notifying the committees of jurisdiction, said Specter. He added: “If we give that kind of a blank check, carte blanche to the executive officials, it would be a terrible, devastating precedent for the future.”

Both the administration and civil liberties groups have poured cold water on the idea, albeit for very different reasons. Dean Boyd, spokesman for the Justice Department’s National Security Division, said that any measure that fails to provide retroactive immunity would “risk losing the cooperation of private partners in the future.”

“In addition, allowing these cases to continue risks the further disclosure of highly classified information,” Boyd said. “Finally, the lawsuits could result in the expenditure of taxpayer resources.”

The ACLU, meanwhile, has condemned the Specter amendment because it believes the measure leaves some loopholes open to the government.

“Unless Congress wholly rejects [the] executive privilege or state secrets claims, there are legal hurdles that could prevent the full hearing of the matter in federal court,” said Tim Sparapani, ACLU senior legislative counsel. “We also oppose having the FISA court making the good faith determination unless outside parties are allowed to argue in front of the secret court, which has never happened before. Otherwise, only one side is represented.”

Lisa Graves, deputy director at the Center for National Security Studies, said the Specter amendment poses another risk: It would set a precedent for letting the carriers ignore FISA in future requests from the government.

“When Congress wrote FISA, it knew you needed a warrant — otherwise firms will always cooperate,” said Graves, a former deputy assistant attorney general at Justice and staffer to the Senate Judiciary Committee. “It’s an inherently coercive arrangement when the government asks for help. That’s why you need a court order.”

But Specter has secured the backing of Democratic colleagues on the Judiciary panel, such as Sheldon Whitehouse (R.I.) and Ben Cardin (Md.), who are also seeking compromise on the immunity question. And although Specter’s amendment failed in committee last December on a 5-13 vote, it won the support of panel Chairman Patrick Leahy (D-Vt.).

Whitehouse is a co-sponsor and has worked with Specter on language in the amendment.

In addition, Dianne Feinstein (Calif.), a key Judiciary Democrat who initially voted against the Specter measure in committee, is generally interested in finding middle ground “between the all-or-nothing approach” on immunity, said Feinstein spokesman Scott Gerber.

Feinstein plans to introduce two amendments of her own: a provision that would grant the carriers immunity only if the FISA court determined they were acting in good faith; and another that would strengthen language in the Senate Intelligence Committee bill to ensure that the FISA court holds exclusive authority over foreign-intelligence surveillance on U.S. soil.

“She’s not taking a line one way or the other regarding the Specter amendment,” added Gerber. “She has looked at it as an alternative, but right now she feels her amendments are the way to go.”

The California Democrat also sits on the Intelligence panel. She voted for that panel’s bill but has since said she wants to use the amendment process to strengthen oversight over the surveillance program and find a compromise on immunity. Two other Intelligence panel Democrats who voted for the measure — Whitehouse and Sen. Bill Nelson (Fla.) — have expressed similar intentions.

When the Senate takes up the bill, the first pending amendment will be the Judiciary Committee’s own FISA bill, which is silent on immunity and would further strengthen the court’s oversight. Liberal Democrats and civil liberties groups prefer that version, and it would also be easier to reconcile with the FISA bill that the House passed last fall, which likewise does not grant immunity. But it would be certain to draw a White House veto.

A drawn-out Senate battle looks likely in any case.

Should the Judiciary amendment fail, some of its provisions are likely to be offered separately, such as language to cut the underlying bill’s sunset provision from six years to four. Two Democrats, Chris Dodd (Conn.) and Russ Feingold (Wis.), are likely to block any bill that contains immunity. Republicans, meanwhile, will try to keep as much of the Intelligence Committee’s bill intact as they can, as will Intelligence Committee Chairman Jay Rockefeller (D-W.Va.), who opposes the Specter language.

If the debate gets bogged down, Senate Majority Leader Harry Reid (D-Nev.) is expected to push for a temporary extension of an administration-backed interim FISA law, passed last August, that expires on Feb. 1. That would allow for additional time for more amendments, most of which are expected to come from the Democratic side. But the longer and messier the FISA fight, the more eager the Senate might be to find compromise on immunity and other amendments, say some aides.