Letterman made several wisecracks on CBS' "Late Show" on Monday about Palin's visit to a New York Yankees game.
He joked that Palin's daughter had sex with third baseman Alex Rodriguez. The joke appeared to refer to 18-year-old Bristol, a single mother. But it was 14-year-old daughter Willow, not Bristol, who had been at the game.
Palin has charged Letterman with making "sexually perverted comments."
On Wednesday, Letterman denied that he would ever joke about sex with a 14-year-old girl. Joking about an 18-year-old? In questionable taste, he said _ but clearly yes.