You may remember Donald Trump once threatened to run on his own if the Republican party treated him badly.

Well now, it’s the Republicans who think Trump is treating the party badly and are talking about rebelling.

One of them is Republican Senator Ben Sasse of Nebraska who was elected in 2014 promising to shake things up in Washington. He was all about confronting the establishment.

Related: What could Obama do to make Republicans run with their tails between their legs?

“And it’s the establishment that is the problem,” he said. “This election must be about saving the country from the establishment.”

You’d think that as an anti-establishment blunt-talker he’d be 100 percent with Donald Trump. But on Facebook on Monday, he announced that he was now 100 percent against Trump.

Sasse is so against Trump that he became the first senator to talk about starting a third party that would focus on issues including defending the sanctity of life, stopping Obamacare, and protecting the Second Amendment.

It seems to be Trump’s apparent ignorance of David Duke &#8211 the former Ku Klux Klan leader who came out in support of him last week &#8211 that pushed some Republicans over the edge. Trump eventually disavowed Duke, but that hasn’t stopped Supremacist groups from campaigning for him without his consent.

And despite Trump’s disavowal of all this, CBS news Political Director John Dickerson says many Republicans flat out don’t believe him. They think he waffled on purpose. As a result, Trump may end up delivering on his signature campaign promise sooner than he thought, as Dickerson points out.

“If there was a wall between Republicans and Donald Trump, it is now 10 feet taller,” Dickerson said.