Republican presidential candidate, former Massachusetts Gov. Mitt Romney signs autographs during a campaign stop at Kinzler Construction in Ames, Iowa on Thursday. (Charlie Riedel/AP)

LE MARS, Iowa – Mitt Romney returned to Iowa Saturday night sounding even more sure of his chances at claiming the Republican presidential nomination than when he left the state the day before.

Stepping into a packed family diner here, Romney told a few hundred supporters: “If I’m the Republican nominee, I’ll be back in Iowa to win the general election and we will win Iowa. We’ll go to Washington with a mandate to make sure we get this country back on the right track. I’m gonna be back in Iowa.”

But Romney, apparently seeking to burnish his anti-immigration credentials before conservative voters, made a comment that one of President Obama’s top political advisers suggested could hurt him in a general election contest.

For the first time, Romney said outright that he would veto the federal DREAM Act, legislation that would provide a pathway to citizenship for certain undocumented immigrants. The former Massachusetts governor previously has been critical of the DREAM Act – and, as governor, he vetoed a similar state law – but previously had not said he would veto the federal law as president.

“If I were elected and Congress were to pass the DREAM Act, would I veto it?” Romney said, repeating the question a voter asked him at a campaign stop in Le Mars. “The answer is yes.”

Romney went on to say he is “delighted with the idea that people who come to this country and wish to serve in the military can be given a path to become permanent residents of this country… I respect and acknowledge that path.”

But, he added: “For those who come here illegally, the idea of giving them in-state tuition credits or other special benefits I find to be contrary to the idea of a nation of law. If I’m the president of the United States, I want to end illegal immigration so that we can protect legal immigration.”

According to a campaign aide, Romney specifically opposes provisions in the measure that would open a path to legalization for illegal immigrants who complete high school and two years of post-secondary education and that would allow states to grant them in-state tuition to public colleges.

David Axelrod, Obama’s top political strategist, highlighted Romney’s comments on Twitter, calling Romney “wrong on principle & politics.”

The DNC’s Senior Advisor for Hispanic Affairs, Juan Sepúlveda, also weighed in, saying in a statement, “Mitt Romney has shown once again that he is out of touch and far to the right of even members of his own party, and that he would not represent the best interest of middle class Americans, those still trying to reach the middle class, and Hispanics in the country.”

Romney’s comments come as recent polls show that Republicans still face a challenge in winning Hispanic support. A recent survey by the Pew Hispanic Center found President Obama leads Romney by 68 percent to 23 percent among Hispanic voters.

Romney’s stop in Le Mars was his first in Iowa since leaving the state after a three-day bus tour. He spent about 30 hours in New Hampshire, holding a spaghetti dinner with supporters Friday night and a breakfast on Saturday morning.

Both events drew overflow crowds, clearly boosting Romney’s confidence just days before voting begins to pick a nominee. At the New Hampshire dinner, Romney said he expected to win not just the nomination, but the White House. “I look forward to getting this job, and I think I will,” he said.

In Le Mars, Romney was introduced by his youngest of five sons, Craig, who called his dad “relentless.”

“My dad is a very competitive guy,” Craig Romney said.

To make the point, he described a Romney family tradition: an annual family triathlon, including a short swim, bike race and run. This past summer, Craig’s wife had been recovering from having her second child and decided to compete in the race.

“All the boys had finished at that point and it was down to my wife and my dad,” Craig said.

“I tripped her!” Mitt Romney playfully chimed in, laughing. “I tripped her!”

The race was in the home stretch, Craig recalled, and his wife had a slight lead over Romney. “In that moment, he decided he was gonna win that race or he was gonna die trying. And you see this fight to the finish, he went for this, he gave it everything he had, he gave it a good kick and he beat her in the end.”

Soon after, Craig said, his father passed out in a lawn chair, and the Romney clan didn’t see its patriarch for the rest of the day.

“He did almost die trying,” Craig said.

This story has been updated.