Florida Sen. Marco Rubio speaks at the Conservative Political Action Conference at National Harbor in Maryland, Feb. 27, 2015. Rubio announced his candidacy for president on Monday. Reuters

U.S. Sen. Marco Rubio of Florida has officially thrown his hat in the ring by declaring his intent to run for president in 2016 to his top donors on Monday. His formal bid is expected Monday night during a “big announcement” at a political rally in Miami. A live stream video of Rubio’s anticipated speech can be watched online via the senator’s website,

Rubio joins GOP U.S. Sens. Ted Cruz of Texas and Rand Paul of Kentucky in officially declaring their bids for the Republican primary. "I do think he's going to try to reach the American people in a way that tells a story of a very different, optimistic, prospective vision for America, that isn't just the doom and gloom that we tend to get an awful lot of the time on our side,” Rick Wilson, a Florida Republican strategist, told NBC on Monday.

A small number of Democrats and about a dozen Republicans have hinted at a run in 2016. Hillary Clinton, whose candidacy was long anticipated, officially announced her bid Sunday. The former first lady and secretary of state failed to secure her party’s nomination in 2008 against then-senator Barack Obama. Former U.S. senator Jim Webb from Virginia, former Rhode Island governor Lincoln Chafee and former Maryland governor Marin O’Malley have all indicated they’re likely to run against Clinton.

Former Florida governor Jeb Bush, Wisconsin Gov. Scott Walker and New Jersey Gov. Chris Christie are among the handful of Republicans who have come out as having an interest in running in 2016.

Rubio, a native of Miami with Cuban roots, was a member of the Florida House of Representatives from 2000 to 2009. He served as its speaker from January 2007 until the end of his term. The GOP senator has opposed President Barack Obama’s 2014 executive actions on immigration offering temporary amnesty to millions of undocumented immigrants living in the U.S. He has also criticized the Obama administration for what he has said was a soft stance on the Russian conflict with Ukraine. Rubio has said he opposes same-sex marriage and does not think climate change is manmade.