We all know that conservatives are skeptical of Mitt Romney, he of the shifting positions on social issues and infamous proclamations of not wanting to return to Reagan-Bush.

But if you need evidence that the attacks on Romney's record at Bain have backfired, and may be doing more to unite conservatives behind Romney more than anything Romney himself could have done, consider this partial list of those who are defending him - and chastising Newt Gingrich and Rick Perry for their "vulture capitalist" attacks:

Rush Limbaugh

Sean Hannity

Laura Ingraham

Jim DeMint

Karl Rove

Mike Huckabee

Rudy Giuliani

The US Chamber of Commerce

The Club for Growth

The Wall Street Journal editorial page

That's quite the conservative Murderers' Row, to borrow a baseball term, that's lining up in an aggressive defense of capitalism, coming in the context of the attacks on Romney's business record.

None of those named above have endorsed Romney. Some - particularly his onetime rivals from 2008 - really don't much like him.

But taken together, the conservative heavyweights are sending important signals to Republican primary voters that the main line of attack being launched against Romney is, in their influential opinions, out of bounds.