JUDY WOODRUFF: Now to presidential politics here in the U.S.
It was a week that saw some contenders exit the stage, while one stumbled his way onto it.
Ray Suarez has our story.
RAY SUAREZ: For Newt Gingrich, this was supposed to be the week he jump-started his presidential hopes. Instead, it turned into a week he might want to forget.
The trouble for Gingrich started Sunday during an appearance on NBC's "Meet the Press," when he dismissed a House Republican proposal to reform Medicare.
NEWT GINGRICH, former speaker of the House: I don't think right-wing social engineering is any more desirable than left-wing social engineering.
RAY SUAREZ: Those comments sparked outrage from conservatives, who thought Gingrich had undercut House Budget Committee Chairman Paul Ryan, the author of the plan.
By Tuesday, Gingrich had called Ryan to apologize, but the damage had already been done.
At one stop in Iowa, Gingrich was confronted by a conservative voter angered by his remarks.
MAN: Get out before you make a bigger fool of yourself.
RAY SUAREZ: The Gingrich camp attempted damage control, issuing a blistering press release blaming the Washington media for the candidate's troubles.
And that memo became fodder for comedians, like Comedy Central's Stephen Colbert.
STEPHEN COLBERT, "The Colbert Report": You know what?
STEPHEN COLBERT: I don't think I have it in me to properly convey the epic genius of this verbal spanking.
RAY SUAREZ: So, he handed off the task to actor John Lithgow.
JOHN LITHGOW, Actor: The firefight started when the cowardly sensed weakness.
RAY SUAREZ: On top of the Medicare episode, Gingrich also had to answer questions about a report that surfaced Tuesday that he and his wife, Callista, had carried a debt of up to $500,000 with the high-end jeweler Tiffany's. Then, at a book signing event in Minneapolis Tuesday evening, Gingrich and his wife had glitter dumped on them by a gay rights activist.
By comparison, former Mass. Gov. Mitt Romney had a pretty good week, thanks to a $10 million fund-raising haul in a single day, Monday.
But an outside Democratic interest group run by former Obama administration officials pressured Romney today with a television ad questioning his support for the GOP Medicare plan.
NARRATOR: Mitt Romney says he's on the same page as Paul Ryan, who wrote the plan to essentially end Medicare. But, with Mitt Romney, you have to wonder, which page is he on today?
RAY SUAREZ: This week also brought fresh signs that the 2012 Republican field was beginning to come into shape.
According to his aides, former Minn. Gov. Tim Pawlenty will officially enter the race next Monday. And former Utah Gov. Jon Huntsman, who is considering a run, made his first trip to New Hampshire.
Huntsman, who recently stepped down as the Obama administration's ambassador to China, was asked in an interview with ABC News if, looking back, he would make the same decision.
JON HUNTSMAN JR. (R), former Utah governor: If there is the prospect that you could get in there and bring about change in a way that helps your country through public service, I'm there.
RAY SUAREZ: The field also lost two potential contenders, with former Ark. Gov. Mike Huckabee and real estate tycoon Donald Trump both passing on bids.
And one of the few remaining undecideds, 2008 vice presidential nominee Sarah Palin, said the motivation was there for a possible run.
SARAH PALIN (R), former Alaska governor: Yes, the fire in the belly, it's there. That's kind of my problem, is that it's such a roaring fire in my belly to preserve and restore all that is good about America, that I struggle with that every single day.
RAY SUAREZ: All in all, a topsy-turvy week for a still unsettled Republican field.