"In GOP Primary Race, Can Steadiness Trump Passion?"

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This is ALL THINGS CONSIDERED from NPR News. I'm Melissa Block.

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Mitt Romney has undergone a transformation in the last week. For almost a year, he tried to portray himself as the grownup, above the fray in the race for the Republican presidential nomination. Now, over the course of two debates and countless Florida campaign stops, the buttoned-up businessman is showing he can get tough, too. This shift has upended the dynamic that's been playing out for weeks between the staid and steady Romney and the passionate, fiery Newt Gingrich.

On this eve of the Florida primary, NPR's Ari Shapiro reports that the new Mitt Romney seems to be winning over many more voters than the old one.

ARI SHAPIRO, BYLINE: Here's a game. I'll play a quote, you guess whether it comes from a supporter of Newt Gingrich or Mitt Romney. Ready? OK. Here's the first one from Christopher Miller at a rally in Jacksonville, Florida.

CHRISTOPHER MILLER: And I think somebody whose main vice is a Diet Coke as a leader of this country is a very interesting concept.

SHAPIRO: He supports Mitt Romney. Ready for the next one? Cliff McKilley attended a rally with his buddy who wore a fed up T-shirt.

CLIFF MCKILLEY: All of them have good qualifications and are capable. But I just step right back there. He's got the fire. He's got the tenacity.

SHAPIRO: McKilley attended a Veterans for Newt rally in Jacksonville. Now to Orlando, and legal researcher Elizabeth Item.

ELIZABETH ITEM: I don't think he'd control himself very well if he became president.

SHAPIRO: She's describing her fears about Gingrich. OK, final round. At this rally in Sarasota, one of the warm-up speakers asked if the crowd was ready to send President Obama back to Chicago. The crowd had someplace else in mind.

UNIDENTIFIED GROUP: Kenya. Kenya. Kenya. Kenya.

SHAPIRO: Kenya, they shouted, as they waited for their man Newt Gingrich. Those supporters reflect the tone and emotional pitch that the candidates themselves have been projecting through the race. Romney attacks Gingrich as unstable.

MITT ROMNEY: It's been highly erratic.

SHAPIRO: And describes himself as a vetted leader. Gingrich attacks Romney as an establishment elitist and brags about his own history of shaking up the status quo.

NEWT GINGRICH: I frankly don't care what the Washington establishment thinks of me because I intend to change them.

(SOUNDBITE OF CHEERS AND APPLAUSE)

SHAPIRO: University of Central Florida political scientist Aubrey Jewett says a lot of Republicans get excited about Gingrich's bare knuckle approach, especially this year.

AUBREY JEWETT: There's a certain segment in the Republican base that still really, really wants someone that's just a fire breather to call Obama out on everything that he's done while in office. And they want also, quite frankly, they want someone that can match the excitement that Obama seemed to bring into his election last time.

SHAPIRO: Like the straight A student who wishes he were the quarterback, the Romney campaign has envied Gingrich's ability to work an audience into a lather. And it's not just Gingrich. Michele Bachmann, Herman Cain and other candidates have the same talent. Gingrich just happens to be the most formidable challenger left. Still, Jewett says Romney has done well enough because voters like the straight A student, too.

JEWETT: Ideally, Republicans would like a candidate that would take sort of both those traits.

SHAPIRO: And that's what Romney has been trying to deliver in Florida this past week. His relentless attacks against Gingrich suggest an act of political jujitsu, redirecting Gingrich's strength, his anger, back against the former House speaker. It even plays out on specific issues such as investments in Fannie Mae and Freddie Mac. This was Romney at last Thursday's debate.

ROMNEY: But have you checked your own investments? You also have investments with mutual funds that also invest in Fannie Mae and Freddie Mac.

SHAPIRO: And on the eve of the Florida primary, that strategy seems to be working. Romney has risen in the polls dramatically. It may have something to do with the millions of dollars his campaign has dumped into statewide advertising here. But it could also reflect this change, that after a year campaigning as the grownup in the race, Romney is telling voters that they don't have to choose between anger and stability, that the former Massachusetts governor can throw a punch, too.

Ari Shapiro, NPR News, Dunedin, Florida.