“It’s been weighing on my mind all week,” he said.

“I’ve never thought about this as a political calculation,” Rubio said of his endorsement. “I’m just sitting back here and watching a president that just got back from overseas — where he told the Russian president to work with him and give him space so he can be more flexible if he gets re-elected.”

“The stakes are so high. We’re not running against John F. Kennedy here,” he said.

“We have to win this election in November. We have to!” he averred. “If we don’t win this election in November — and we get four more years of Barack Obama — I don’t know what that means … But I know it ain’t good.”