National Republican Senatorial Committee (NRSC) Chairman John CornynJohn CornynKey Senate Republican offers dim outlook for Trump budget Overnight Cybersecurity: Flynn refuses to comply with Senate subpoena | Chaffetz postpones hearing with Comey | Small biz cyber bill would cost M | New worm spotted after 'Wanna Cry' Trump budget to call for 0 billion in Medicaid cuts MORE said Monday that his endorsement of Gov. Charlie Crist in Florida's GOP Senate primary was "selfish" and that the committee will not stand in Marco RubioMarco RubioDHS extends protected status for Haitians for six months Congress should let local communities set their own PACE Rubio: ‘People got what they voted for’ MORE's way.

Cornyn (R-Texas) said he stuck by the endorsement, but he also began minimizing it, now that it looks like Crist may well lose the primary. Recent polls have shown Rubio stealing virtually all the momentum in the race and opening a lead over Crist.

"Selfishly, given the limited resources we have and the national scope of our responsibilities here, I didn't want to have to spend any money in Florida if we didn't have to," Cornyn said. "So Charlie Crist seemed like the ideal candidate. This had nothing to do with Marco Rubio, whom I subsequently met and have a lot of respect for."

Cornyn emphasized that he endorsed Crist before it was clear there would be a difficult primary. But he also pointed out that Crist's candidacy and fundraising ability may have scared away top Democrats like state Chief Financial Officer Alex Sink.

He said the committee thinks Rubio would beat Rep. Kendrick Meek (D-Fla.) and won't do anything to oppose Rubio in the primary.

"It doesn't mean we're going to be spending any money in the primary; it doesn't mean we're going to be saying anything bad about Marco Rubio," Cornyn said.