This USAToday article makes it certain that Fred Thompson will enter the race:

Politician-turned-actor Fred Thompson has been coy with audiences as he flirts with a bid for the Republican presidential nomination.

In an interview with USA TODAY, however, the former Tennessee senator not only makes it clear that he plans to run, he describes how he aims to do it. He’s planning a campaign that will use blogs, video posts and other Internet innovations to reach voters repelled by politics-as-usual in both parties.

“I can’t remember exactly the point that I said, ‘I’m going to do this,’ ” Thompson says, his 6-foot, 6-inch frame sprawled comfortably across a couch in a hotel suite. “But when I did, the thing that occurred to me: ‘I’m going to tell people that I am thinking about it and see what kind of reaction I get to it.’ “

However, if you read a bit further down the article, David Keene of the ACU doesn’t seem too impressed:

Some skeptics question whether Thompson has the drive for a national campaign. “He didn’t have a particularly distinguished Senate career, though that has never been a bar to anybody else being president,” says David Keene, president of the American Conservative Union, who isn’t supporting any candidate. “The book on him is he’s lazy. I don’t know whether that’s true or not.”