For their part, McCain and his allies maintain he will be prepared for whatever might confront him in the primary.

“There has been no stronger opponent of President (Barack) Obama’s feckless and failed foreign policy than Senator John McCain,” McCain spokesman Brian Rogers said. “He’s proud of his conservative record of small government, low taxes and a strong national defense, and would match that record against anyone’s.”

Sen. Jeff Flake, R-Ariz., who already has endorsed McCain for re-election in advance of his announcement, pointed out that McCain in 2010 was able to smash a conservative primary challenge from former Rep. J.D. Hayworth.

“He’ll run as if everybody is running against him — he runs hard — but I think he’ll be fine because, overall, he has a very conservative record,” Flake said. “We saw what happened last time: All the polls that showed him vulnerable, but in the end, he won big in the primary and he won big in the general election. He knows how to run campaigns.”