Sen. Marco Rubio, R-Fla., is endorsing former Massachusetts Gov. Mitt Romney to be the GOP presidential nominee.
    
Rubio previously said he would stay neutral in the race, but has now changed his tune.
    
He says it's clear Romney will win the nomination and that continuing the primary fight will only damage efforts to beat President Barack Obama.

"The quicker we can get this campaign on that focus -- focused on the president's record, on the alternative that we offer -- the better off we're going to be as a movement but also the better off the country's going to be," Rubio told Fox News.

Last week, former Florida Gov. Jeb Bush also announced he was backing Romney, and former President George H.W. Bush is expected to announce his support Friday.
    
Meanwhile, Rubio -- a freshman senator and Tea Party favorite -- has been mentioned as a potential vice-president pick. He dismissed the idea, saying his focus remains on the Senate.