If this report from Taegan Goddard is right, it might be:
Red State: "I am told quite reliably that in a meeting today on Capitol Hill, Republican Senators began to rapidly move toward concessions on health care because they are afraid they cannot hold their members. Some Republicans are now thinking of supporting a government program."
It's hard to believe but, according to the Kansas City Star, former Senate Majority Leader Bob Dole (R-KS) is urging Republicans to pass the bill over the objections of current Senate GOP Leader Mitch McConnell (R-KY).
Well, it's not that difficult to believe. Dole's been urging Republicans to come to a bipartisan consensus (ie: give up their opposition and vote for the Democrats' overhaul plan) since at least the end of August. Nor is it that surprising that a few Republicans are ready to roll over: Republicans like Chuck Grassley have been itching to vote for health-care reform for years. For a number of Republicans, the policies up for debate have never really been the issue. The sole goal for the GOP those legislators was to deal Obama political defeat. By no means do I think Republican support is sure thing. But now that the CBO has weakened the GOP's case for opposition, it wouldn't at all surprise me if a number of them defected.
Update: Seems I read this far too quickly. As a number of commenters note, Red State already updated to say that the rumors of Republicans caving are "overblown."