Sen. Marco Rubio announces entry into the presidential race

Sen. Marco Rubio (R-FL) formally announced on Monday evening that he would campaign for president in 2016, rushing to cast Democrat Hillary Clinton as "a leader from yesterday."

"Yesterday is over," he said. "And we're never going back. We Americans are proud of our history, but our country has always been about the future."

Rubio peppered his speech with disparaging references to the Affordable Care Act, as well as President Barack Obama's recent proposed nuclear agreement with Iran and his meeting with Cuban President Raúl Castro.

The senator also portrayed the upcoming election as a "generational choice."

"I've heard some suggest that I should step aside and wait my turn. But I cannot," he said. Because I believe our very identity as an exceptional nation is at stake, and I can make a difference as president."

The announcement came a day after he denounced Clinton in an interview with ABC News host George Stephanopoulos.

"The jobs of the 21st century require different skills and more education than in the past," he said. "We have people from yesterday -- leaders that are still grounded in the 20th century who think if we just pour more money in our existing higher education system, we'll get a 21st century result. It isn't true anymore."