Rubio plugs GOP Medicare plan

He touted the GOP's Medicare plan, spearheaded by Rep. Paul Ryan (R-Wis.).

"Republicans have offered a detailed and credible plan that helps save Medicare without hurting today’s retirees," Rubio said. "Instead of playing politics with Medicare, when is the President going to offer his plan to save it? Tonight would have been a good time for him to do it."

The GOP's Medicare plan polls poorly, and Republicans have not taken any real steps to put it into action. The proposal would partially privatize the Medicare program, so that seniors would choose between the existing program or subsidies for private insurance.

Democrats and some healthcare economists say that approach would drive healthy, inexpensive people out of traditional Medicare, eventually driving up premiums for the program and pushing more and more seniors into the private market.

Rubio also took a shot at the Affordable Care Act, specifically its employer mandate.

"Obamacare was supposed to help middle class Americans afford health insurance,' Rubio said. "But now, some people are losing the health insurance they were happy with. And because Obamacare created expensive requirements for companies with more than 50 employees, now many of these businesses aren’t hiring.  Not only that; they’re being forced to lay people off and switch from full-time employees to part-time workers."