ROBERT SIEGEL, HOST:
The Republican presidential contest has been a roller coaster ride for Florida Senator Marco Rubio. He was up in Ohio, a third- place showing, and then down in New Hampshire at fifth. Now comes South Carolina. The state's GOP primary is Saturday. NPR national political correspondent Don Gonyea reports.
DON GONYEA, BYLINE: In many ways, South Carolina has already given Rubio's campaign a boost, thanks in part to the state's popular governor Nikki Haley.
NIKKI HALEY: We need to show that South Carolina makes president and that our next president will be Marco Rubio.
GONYEA: That's in Greenville this morning. Haley and South Carolina's very popular U.S. Senator Tim Scott have both now endorsed Rubio. It's a potent one-two punch. And for Rubio, it's another way to tell voters who watched him stumble in New Hampshire that he deserves a close look.
MARCO RUBIO: I'm here today to ask you for your vote because I am as conservative as anyone running in this race, but I am a conservative that can win. That's a big deal.
GONYEA: He's drawing good crowds and seems looser on the stump than he did in New Hampshire where he spent much of his time on the defensive after a weak performance in a debate. He always tells the story of his Cuban immigrant parents who worked as a bartender and a maid.
RUBIO: The most important thing of all is they were able to leave all four of their children better off than themselves. That story has a name, it's called the American dream.
GONYEA: He makes a generational pitch and deflects criticism that he's too inexperienced, joking that at age 44, he feels 46. In his speech, the main focus of his attacks is President Obama.
RUBIO: Barack Obama's a terrible commander-in-chief. He is gutting our military. It's not an exaggeration.
GONYEA: And he accuses the president of not doing nearly enough to defeat ISIS.
RUBIO: They have to be defeated. They have to be defeated militarily. How are we going to do that if we continue to weaken our military?
GONYEA: It's a pitch that plays well in a state where a large number of voters have ties to the military. One thing that continues to haunt Rubio, though, is his bid three years ago with a bipartisan group of senators to overhaul immigration law. The bill failed and was immensely unpopular with Republicans. Rubio has since disavowed it as well, but the topic keeps coming up. Here's David Ball, an undecided voter, at a Rubio event earlier in the week.
DAVID BALL: I need to hear what his immigration status is. That's the biggest thing that I have issue with him 'cause he seems to have vacillate back and forth on some of those issues.
GONYEA: At the same event, 61-year-old Henry Vogler is firmly in the Rubio camp.
HENRY VOGLER: It'd certainly be nice to win. But I think if he, you know, if he gets into the top three, I think, you know, I'd be happy.
GONYEA: Top three is good enough.
VOGLER: Top three is good enough, yeah.
GONYEA: Polls would indicate that winning South Carolina outright is way out of Rubio's reach. Trump has a solid lead. For Rubio, winning would likely mean finishing first among those candidates who've been dividing up the anti-Trump and anti-Cruz vote. But his big endorsements also bring with them heightened expectations, so he'll also have to meet them to gain momentum going forward. Don Gonyea, NPR News, Charleston. Transcript provided by NPR, Copyright NPR.