Rubio Believes He Must Be 'Doing Something Right'

Sen. Marco Rubio today brushed off recent attacks by his GOP rivals, saying he must be "doing something right," and expressing confidence despite what he called the "unusual set up" in today's New Hampshire primary.

"It's great to be targeted because that means you're doing something right," the Florida Republican told "Good Morning America."

"People don't waste time or money attacking someone who isn't doing something well."

New Jersey Gov. Chris Christie repeatedly challenged Rubio at Saturday's debate, hosted by ABC News, saying Rubio "memorized 25-second speech."

Despite Christie's attacks, Rubio believes he had "a very strong debate," and doubts it will affect people's opinion.

Rubio admitted this morning he is uncertain where he will place in the Granite State, but he believes he will "finish strong."

"I know Trump is a clear front-runner, he's been in first place since June," he said. "We've got some people that haven't campaigned anywhere else but here, their whole campaign is built here. So it's a pretty unusual set up."

The GOP hopeful went on to say he gives the Republican Party the best chance to do three things: "To unify, to grow and to win."