House Speaker Paul D. Ryan shut the door Thursday on speculation that he would become a unity candidate for president at the Republican convention this summer in Cleveland, saying that the nominee will come from those candidates who have run campaigns.

Ryan for the first time acknowledged the likelihood, however, that none of the Republican candidates for president would accumulate the necessary delegates to secure the nomination in advance of the mid-July gathering.

“It’s not going to be me, it should be somebody running for president,” the Wisconsin Republican said at his weekly news conference. He told reporters that he cursed out former House Speaker John A. Boehner at an event Wednesday night in Washington, following Boehner’s comments at a Florida speech that morning in which he suggested that Ryan would be the right candidate if the convention deadlocks.

“I saw Boehner last night and I told him to knock it off,” Ryan said.

He said that he will study the rules and processes for how a contested nomination process would work for the Republican National Convention. In Cleveland, Ryan and Senate Majority Leader Mitch McConnell (R-Ky.) will serve as co-chairmen — a position that Ryan admitted Thursday that he did not know came with the job of speaker when Boehner passed him the gavel in October.

“My goal is to be dispassionate, and to be Switzerland, to be neutral and dispassionate and to make sure the rule of law prevails,” Ryan said, “and to make sure that the delegates make their decision however the rules require them to do that.”

It was a stark change in tone for Ryan. In the past two months, he has mocked reporters asking about his role overseeing a potentially confrontational floor fight between supporters of front-runner Donald Trump and movement conservatives who are pushing a “Never Trump” campaign to find an alternative nominee in Cleveland.

After Tuesday’s victory by Ohio Gov. John Kasich (R) in his home state, Trump’s path to a bare majority of delegates ahead of the convention became more difficult. Sen. Ted Cruz (R-Tex.) is the only other candidate in the race who has a mathematical chance at a majority of delegates, but his path is even steeper than Trump’s.

That’s prompted Ryan to recognize that he and McConnell are increasingly likely to have major roles in what previously had been considered merely ceremonial positions overseeing the nominations for president and vice president.

“Nothing has changed other than the perception that this is more likely to become an open convention than we thought before,” Ryan said Thursday. “So we’re getting our minds around the idea that this could very well become a reality, and therefore, those of us who are involved in the convention need to respect that.”