We talked about his controversial Social Security reform plan, which would slow down future benefits by indexing them to inflation rather than wages, while providing for add-on private savings accounts with a government match, Lower benefits? Isn't that the proverbial third rail of politics? Not according to Thompson. He said big problems ought to be tackled: "If you can't do the right thing, say what you believe and what everybody really basically knows, why do it? Why bother? Life is too short for the aggravation."

Thompson wants to tell the truth about Social Security and force everyone else in the game to respond. This issue is a real character-building definer for Fred Thompson. No one else on the campaign trail, in either party, is willing to discuss Social Security in such frank terms.

But that's the revitalized Fred Thompson. The more I challenged him, the more animated he became. He simply refused to stand down.

Some people say Thompson doesn't have the fire in his belly to go the distance. I don't think that's true. And I'm not picking or endorsing any candidates here. But Thompson has an honest, clear, straightforward message of economic freedom and problem solving.

Then I brought up the CNBC-Wall Street Journal debate of a few weeks ago, when Thompson slammed Rudy Giuliani. I asked if he intended to continue to pound Giuliani on the campaign trail. He said, "I haven't pounded all day." And yesterday? He replied: "Well, we're pointing out some policy differences. (Giuliani) believes in federal funding for abortion. He went to court to stop our bill outlawing sanctuary cities. He's never met a gun-control bill he didn't like."

A sharp-edged Fred Thompson.

Can he win? His campaign strategists told me they are pouring tons of money into Iowa advertising. They see a strong opportunity for a Thompson surge in the state, undermining Romney and inflicting damage on Giuliani. Walking off the set, Thompson told me this election will be about peace and prosperity. And he intends to fight hard.