Senator Marco Rubio of Florida announced his candidacy for president Monday morning in a call to donors, becoming the third Republican to officially enter the 2016 contest.
Mr. Rubio will make a formal announcement Monday evening here in which he is expected to present himself as the embodiment of generational change who can unite the Republican Party’s factions and offer economic solutions for the 21st century.
At 43, the youngest candidate in the rapidly growing 2016 presidential field, Mr. Rubio is expected to cast himself as a forward-looking, next-generation leader — and an implicit contrast with both Jeb Bush, 62, whose family has dominated Republican politics for nearly three decades, and Hillary Rodham Clinton, 67, the wife of a former president and the likely Democratic nominee.
Mr. Rubio joins his Senate colleagues Ted Cruz of Texas and Rand Paul of Kentucky, who both have announced their candidacies. Other Republican hopefuls, including Mr. Bush and Gov. Scott Walker of Wisconsin, are also preparing to officially enter the race.
Mr. Rubio is expected to campaign on themes that emphasize American greatness and the American dream, an optimistic, aspirational message that he outlined in his newly released book, “American Dreams.”