House Speaker Paul Ryan (R-Wis.), center, at a news conference with Rep. Cathy McMorris Rodgers (R-Wash.) and House Majority Leader Kevin McCarthy (R-Calif.) (Chip Somodevilla/Getty Images)

House Speaker Paul D. Ryan (R-Wis.) issued a public warning to Donald Trump over the tenor of his rallies and the behavior of his supporters, the third time the GOP’s highest-ranking official delivered a rebuke to the Republican presidential front-runner in three months.

While the speaker placed some blame on liberal protesters who have tried to disrupt Trump rallies, Ryan said the candidates have an obligation through their speeches to keep a calm environment in these settings —a clear shot at recent raucous Trump events that have included fights and other caustic showdowns.

“All candidates have an obligation to do what they can do to try and provide an atmosphere of harmony, to reduce the violence, to not incite violence and to make sure that we are appealing to people on their best ideals,” Ryan told reporters Tuesday after the weekly meeting of the House Republican Conference.

In December, after the terrorist shootings in San Bernardino, Calif., prompted Trump to call for a ban on Muslims entering the country, Ryan rejected that proposal as “not what this party stands for.” Just two weeks ago, after Trump struggled to denounce support he was engendering from white supremacists, Ryan said that Republicans do “not prey on people’s prejudices.”

[Paul Ryan rejects Trump’s KKK comments, but not his candidacy if he wins nomination]

Ryan said the protesters at Trump’s rallies also have contributed to the level of violence and rhetoric at the events, a line that the presidential candidate has uttered many times in the past few days by blaming liberal supporters of Sen. Bernie Sanders (Vt.).

“It’s pretty clear that there’s a concerted effort by people on the left to disrupt these rallies, to disrupt these events, and that needs to be condemned,” Ryan said.

He reiterated that Republican voters will decide who the nominee is for the general election and that he will support that individual. “This is not our decision to make,” Ryan said, stressing that his effort is focused on forging an agenda for the eventual nominee and not helping to select that person.

“And that is what we can control. All of these other things on the top of the ticket are things that are not within our control,” Ryan said.

In the past 10 to 12 days, Ryan has spoken with Trump and the other three remaining Republican presidential candidates — Ohio Gov. John Kasich and Sens. Ted Cruz (Tex.) and Marco Rubio (Fla.) — about his emerging agenda for the fall elections.

“Trump called us. We called him back, walked him through our agenda project,” Ryan said of the discussion with a candidate whose anti-trade, higher-tax positions seem at odds with those of the speaker. “We got very good reception from all four of those candidates, including Trump.”