Seth Masket believes so:
In The Party Decides, Cohen et al. talk about the importance of endorsements by out-of-group elites. … The example we have today is that the bulk of Republican members of Congress who served with Gingrich are now backing Romney. It wouldn't be terribly impressive if they had backed Gingrich — we'd have expected that kind of loyalty to the former Speaker. But the fact that they know him well and are refusing to back him is very meaningful.
David Frum had one of my favorite quotes on the subject: "Suppose it were Gingrich v. Obama. And suppose we restricted franchise to Republicans who served in Congress 1978-1998. It'd be a close vote."