Marco Rubio Believes He Must Be ‘Doing Something Right’

"It's great to be targeted," the Florida Republican told "Good Morning America.”

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

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."