RNC chair Reince Priebus is facing backlash after suggesting that former Republican presidential hopefuls considering a 2020 White House bid may face challenges if they refuse to support Donald Trump.

“People who agreed to support the nominee, that took part in our process, they used tools from the RNC,” Priebus told John Dickerson CBS News’ Face the Nation. “Those people need to get on board. And if they’re thinking they’re going to run again someday, I think we’re going to evaluate the process…and I don’t think it’s going to be easy for them”

In a fiery rebuttal, John Weaver, chief strategist for former GOP presidential candidate and current Ohio Gov. John Kasich, slammed Priebus.

“(Kasich) will not be bullied by a Kenosha political operative that is unable to stand up for core principles or beliefs,” Weaver said in a statement referring to Priebus’ Wisconsin hometown. “In fact, Reince should be thanking the Governor for standing for an inclusive, conservative vision that can actually win a national election and improve our country.”

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During a pre-taped interview with Meet the Press, Kasich addressed Priebus’ earlier suggestion that Republicans who have not backed the party’s nominee will ultimately help Clinton get elected.

“I don’t take my cues on what I’m going to do in the public arena or anywhere else from him. I’ll decide what I want to decide, and then I’ll let people know when I want to,” Kasich said.

It isn’t the first time Kasich’s team, which is sharply critical of Trump’s rhetoric and concerned about his candidacy’s lasting effect on the future of the Republican party, has sparred with the RNC chair. Last Spring, Priebus called Trump the likely GOP nominee even though Kasich was still in the GOP primary race and before any Republican candidate clinched the needed 1,237 delegates.

“I was still in it and I think he dissed me, and I think it’s inappropriate,” Kasich told the Washington Post after suspending his White House bid.

And with less than eight weeks before the general election, Kasich has yet to endorse Trump even though he signed the RNC’s pledge to support the eventual nominee.

The governor maintains that he will not vote for Hillary Clinton, who he says is a “top-down person” who has an “enthusiasm gap” among voters in Ohio, but has signaled that a Trump endorsement is far-fetched.

“I’m unlikely to cast that vote [for Trump], the chances are minuscule,” Kasich told Todd. Kasich added that he’d have to see a “fundamental change” in Trump’s policies and behavior before he could support the nominee.

Last week, in a meeting that raised eyebrows among GOP operatives, Kasich made his case for the Trans-Pacific Partnership during a White House visit with President Obama.

When asked about the Trump’s assertion that President Obama was born in the United Stated, Kasich, standing behind the White House podium in the West Wing’s Press Briefing Room, quipped, “Bruce Springsteen has to be really happy because born in the USA’s probably gonna sell a lot more albums.”