Cruz won't promise to stay out of primaries
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Sen. Ted CruzRafael (Ted) Edward CruzGOP senators introduce Trump's plan to claw back billion in spending Pro-Trump super PAC raises .5 million in 6 weeks Trump has exposed Democratic hypocrisy on prison reform MORE (R-Texas) on Thursday didn't rule out involvement in GOP primaries this year against incumbent Republican senators.

Cruz said he had made no "ironclad promise" to stay out of the primaries.

"What I have said is that I'm likely going to stay out of incumbent Republican primaries," he said. "I haven't put that in concrete." 

A fundraising email Cruz wrote for the Madison Project emerged this week. The group has backed Republican candidates running against Senate GOP Leader Mitch McConnellAddison (Mitch) Mitchell McConnellGiuliani: White House wants briefing on classified meeting over Russia probe GOP senators introduce Trump's plan to claw back billion in spending The Hill's 12:30 Report — Sponsored by Delta Air Lines — Trump now says Korea summit could still happen June 12 MORE (Ky.) and Sen. Pat Roberts (Kan.).

Cruz had told other Republican senators that he wouldn't help outside groups targeting his opponents, and he said the email for the Madison Project had been written last April, before the conversation had taken place.

But Cruz, who irritated his colleagues earlier this month with a filibuster on legislation to raise the debt ceiling, said nothing is certain.

"Things can change in politics," he said.

He also criticized the National Republican Senatorial Committee for its involvement in GOP primaries. Cruz is the vice chairman of the NRSC, though he has often worked at cross-purposes with the group.

"I disagree with what the NRSC has done there," he said. "When I took on the role leadership had told me that they'd learned the lessons from 2010 to stay out of primaries."

Cruz disagreed that he was causing problems for other GOP senators — and blamed leadership.

"I don't want to throw any Republicans under the bus," he said, criticizing McConnell and Sen. John Cornyn (R-Texas) for whipping Republicans to vote for the procedural motion to get to a final vote on the debt ceiling bill. "To be clear, it was Republican leadership that was looking to throw Republicans under the bus."

He refused to say whether or not McConnell should remain leader of the Senate Republicans, saying that decision was up to the conference but that he "strongly disagreed with some of the decisions Republican leadership has made in the last year," and wouldn't say whether he planned to vote for Cornyn in his primary against Rep. Steve Stockman (R-Texas). Early voting has begun for that primary.

Cruz's remarks came at a breakfast sponsored by Politico.