Wonder what's going to unite conservatives around Sen. John McCain? It all comes down to the word "liberal."

Mississippi Gov. Haley Barbour gave a preview after endorsing McCain yesterday in Washington: "Barack Obama is to the left of Big Bernie Sanders, and he's a socialist. Bernie Sanders is a socialist."

The basis for that judgment is the National Journal, which annually ranks senators' voting records and deemed Obama's the most liberal in 2007 — even more than Vermont's Bernie Sanders, an independent who caucuses with Democrats but is a self-professed socialist.

It was clear the National Journal ranking was going to come back to haunt Obama, just as the magazine's list in 2004 hurt John Kerry. But McCain appears ready to make far more use of it than the Bush campaign did four years ago.

"I promise you that by the end of this campaign that'll be right there on your refrigerator on one of those magnets," McCain campaign manager Rick Davis told reporters last month.

In yesterday's endorsement press conference, neither Barbour nor Georgia Gov. Sonny Perdue gave a stirring defense of McCain, but both had plenty to say about Obama.

"John McCain is not as conservative as Haley Barbour. If John McCain was running against Fred Thompson, or Mike Huckabee, or Mitt Romney, or Rudy Giuliani, that's one thing. But if John McCain is running against Barack Obama or Hillary Clinton, there's absolutely no question who the conservative candidate is," Barbour said.

He said it was "wishful thinking by the news media" that conservatives won't support McCain.

Perdue said the the key for him was a meeting the Republican governors had last week with McCain. Perdue said he came away with an appreciation for McCain's respect for federalism.

— Stephen Dinan, national political reporter, The Washington Times