Rubio on track for 2016 run

• A source close to Sen. Marco Rubio says he is on track to run for president in 2016


• This comes in the wake of mentor and former Gov. Jeb Bush saying he's 'exploring a bid'


• The source says Bush's entrance changes the race's dynamics 'but not Marco's thought process'

Washington (CNN) -- Florida Sen. Marco Rubio is on track to run for President in 2016 even if Jeb Bush also jumps into the race, a source close to Rubio says.

The source told CNN that a Bush candidacy -- increasingly likely after the former Florida governor said in a Facebook post Tuesday that he will "actively explore" running -- changes the dynamics of the race "but not Marco's thought process."

'Inside Politics' forecast

Biggest news yet in the race for 2016?

McConnell backing Paul in 2016

Rubio has invited supporters to a Jan. 23-24 retreat in Miami Beach, where his top aides and donors could formalize his plans for 2016.

A run for president would be a big risk for Rubio, a 43-year-old former Florida House speaker who looks like a sure bet to win a second term in the Senate in 2016.

He's making the moves of a presidential contender. Rubio campaigned with GOP candidates in the 2014 midterm election. He has a memoir set for release in January. And he's working with incoming House Ways and Means Chairman Paul Ryan (R-Wis.) to craft health care legislation meant to be an alternative to Obamacare.

He's also been increasingly vocal on foreign policy issues -- potentially setting up a clash with leading Republican contenders like Kentucky Sen. Rand Paul, who has called for less U.S. intervention overseas.

Rubio, though, would share one problem with Bush: He's championed an overhaul of U.S. immigration laws, a position that has fallen out of favor with much of the GOP base.