Fred Thompson Says Mettle Will Be Proven on the Campaign Trail

Newly announced GOP presidential hopeful Fred Thompson brushed aside jabs about his energy and work ethic today, two days after his official entry into the race.

"I guess that's a question that will [be] resolved on the campaign trail," Thompson said in an exclusive interview on ABC's "Good Morning America."

Thompson also spoke frankly about concerns over his health and the role his wife will play in the campaign.

Hoping voters will cast him in the role of a lifetime, the former actor, lawyer and politician finally announced his candidacy for president Wednesday night on "The Jay Leno Show."

Saying he wants to make the world a safer, more secure place for his children and grandchildren, Thompson is already coming in second place in many polls, behind former New York City Mayor Rudy Giuliani.

His campaign kicked off with the tag line: "the Hunt for Red November."

But as the 65-year-old tools around Iowa in his kid-friendly campaign bus, complete with a diaper-changing table for his 10-month-old son, Samuel, serious questions loom about his candidacy.

Does He Have What It Takes?

Some question his work ethic. While he was a senator from Tennessee, Thompson was not known as a workhorse. A recent Newsweek cover story about Thompson is titled "Lazy Like a Fox."

And in the Republican debate Wednesday night, several of his rivals ridiculed his late entry into the race. "What's the hurry? Why not take more time off?" Gov. Sam Brownback said.

Thompson told "GMA's" Diane Sawyer he considers himself "deliberate," but said that trait has served him well politically in other campaigns where he was down in the polls, but rallied to win.

Thompson, who is in remission from lymphoma, says he gets regular checkups; the last one showed no sign of cancer.

He has also faced criticism about his 40-year-old wife, Jeri, the glamorous former Republican operative whom many Thompson staffers this summer reportedly said was too controlling of the campaign.

"She is smart. I confide in her and she helps me in the things I want to do," Thompson said of his wife. "If some people who got their feelings hurt anonymously want to go after her instead of me, well, there's nothing I can do about that."