Jack Balkin has an answer,
Look, if it's that important, there's a simple answer: pass the bill without telecom immunity. Then come back and introduce immunity in a separate bill. If you've got the votes for it, fine. If not, too bad. I'm against immunity myself — though hardly hellbent on the subject — but whichever way the vote went, in the meantime we'd have the FISA extension and surveillance could continue normally.
But that's not on the table. The supposed grownups in the GOP are, apparently, perfectly happy to play around with "life and death" if it's in the service of a bit of demagogic brinksmanship over telecom immunity. Why?
Mike McConnell's call for immunity for telecom companies in today's Washington Post would be far more persuasive if we didn't recall why the issue arises in the first place. The Bush Administration repeatedly violated FISA and told telecom companies that it was ok to do so based on a crazy constitutional theory that the President couldn't be bound by the law.
Of course telecom companies will be less likely to cooperate in the future with an Administration whose legal advice has proven to be so unreliable. But giving them immunity whenever they recieve bad advice from the White House gives the White House no incentives to stay within the boundaries of the law. As I have pointed out before immunity provisions make it much easier for an untrustworthy White House to cover up its misconduct. In essence, the President wants legal assurances that nobody will have incentives to reveal what his subordinates did and what he asked the telecom companies to do.