But Rubio has not been shy about his critique of the president, especially while he was campaigning for Romney last year.

"He is a bad president," Rubio said bluntly in his speech at the Republican National Convention in Florida last summer. "Under Barack Obama, the only change is that hope is hard to find."

Observers expect no less from his speech on Tuesday night.

Supporters in his hometown of West Miami will be watching closely. Rebeca Sosa is organizing a Rubio watching party at the same rec center where he first saw his future wife.

A few blocks away on the main drag of West Miami, an older man is holding a sign in front of Versailles Restaurant as the cars pass by on Eighth Street.

"Marco Rubio for president 2016," it says.