Romney appeared on Tuesday's edition of "Late Show with David Letterman."
Asked if he would run for president in 2012, Romney replied, "No plans for that at this point -- I'll keep the door open."
The answer prompted Letterman to joke: "He's running, of course he's running ... I can tell by the cologne."
"Now what about that Sarah Palin -- she's not ready to be president, is she?" Letterman pressed.
"She's terrific," Romney said. "She really is, she's terrific. She's got energy, passion -- by the way, you know, be careful what you say about her, by the way ... . She has a rifle, you know."
Letterman also questioned Romney about an alleged altercation he got into with a passenger on a flight back from the Winter Olympics in Vancouver.
"A guy beat you up on the plane. Do I have this right?" the host said.
"Not exactly right," Romney said. "Well, there's not a lot to add. The fellow in the seat in front of my wife put his seat back during the takeoff procedure and, as we've all heard 10,000 times, 'Please put your tray table and the seat back in the upright and locked position.' And so I tapped him on the shoulder and I reminded him of that direction, and he became somewhat agitated, and they removed him from the airplane and he didn't like that, by the way, and gave me a good swat and he broke my hair."
Copyright 2010 United Press International.