Christie got into a heated debate last week with former White House doctor Connie Mariano who said she was concerned the governor might die in office if he were elected president.
Mariano was commenting on Christie's appearance Monday on "Late Show with David Letterman," in which the governor ate a doughnut while joking about his weight but Christie also said he is "the healthiest fat guy you've ever seen in your life."
Speaking with reporters Wednesday, Christie called Mariano "just another hack who wants 5 minutes on TV," and told her to "shut up."
In a round table appearance on ABC's "This Week," Karl said he thinks people should "give [Christie] a break" about his weight.
"But I will say this. If he seriously takes on the issue of his own health and his weight the way ... Mike Huckabee [did when he] first became a national figure as governor of Arkansas [and] he dealt with his own weight [and] lost 100 pounds," Karl said. "If [Christie] kind of turns this into ... a political version of 'The Biggest Loser,' Christie can gather even more support. So many Americans relate to what he is dealing with. So many of us are overweight."
Also in the round table discussion, Republican strategist Nicolle Wallace said Christie should stop telling people to "shut up" if he wants to run for president.
He's "from New Jersey, and so I think that's New Jersey for, you know, 'Give me a minute,' " she said.
She said that Christie addressing his weight with Letterman "was a very skillful political move, turning your own vulnerability or something you feel vulnerable about into something that you make fun of before anyone else does is political genius. But then it didn't take him 24 hours to reveal a rather thin-skinned side of the issue."
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