Marco Rubio on Monday repeatedly defended his decision to repeat one of his key talking points from the Saturday debate, which led to widespread repetitive criticism from the press.

Rubio was hammered by Gov. Chris Christie to reverting several times to a canned line in which he said President Obama knows exactly what he's doing in the White House, and that Republicans must stop him from changing America. But Monday morning, Rubio said he'd keep repeating that line.

"What I said at the debate over and over again is what I'm going to say right again. Barack Obama is changing America. And I think the question is why more Republicans aren't saying that," Rubio said Tuesday morning as the polls opened in New Hampshire, during an interview on "Fox and Friends."

"If you don't understand the difference between us and the Democrats isn't just a few little issues, but they have a very different view of what America should be and what our government should be," he added.

Rubio's decision to play up the savvy Obama may be a reaction to criticism that the country could elect another one-term senator to the White House, as it did with Obama.

Going in to the New Hampshire primary, many polls have Rubio in second place, behind Donald Trump but leading the rest of the pack.

"I'm not in this campaign to attack Republicans. If we're not unified at the end of this process Democrats are going to win," Rubio added. "I think every time the Republicans go after each other in an ugly way, the Democrats cheer because we're doing the job for them. They love seeing this stuff."