GOP Chairman Reince Priebus appeared on Face the Nation with a threat for Sen. Ted Cruz, Gov. John Kasich, and former Gov. Jeb Bush: get on the Trump train or expect a lock-out in 2020.

“Those people need to get on board,” he told CBS’ “Face the Nation.” “And if they’re thinking they’re going to run again someday, I think that we’re going to evaluate the process – of the nomination process and I don’t think it’s going to be that easy for them.”

If any statement could do more to damage the already-fragile Republican Party, I don’t know of one. It strains my imagination to see how Trump has so thoroughly corrupted and co-opted the GOP to his own machine. It almost seems like he has something damaging on Priebus, the way the chairman carries water for the billionaire, who was barely taken seriously only a year ago.

Trump has become the Establishment incarnate.

The very first question in the very first debate asked all the candidates if they would support the eventual nominee. Fox News’ Brett Baier questioned Donald Trump, the only participant who openly refused to make that pledge.

BAIER: You can’t say tonight that you can make that pledge? TRUMP: I cannot say. I have to respect the person that, if it’s not me, the person that wins, if I do win, and I’m leading by quite a bit, that’s what I want to do. I can totally make that pledge. If I’m the nominee, I will pledge I will not run as an independent. But — and I am discussing it with everybody, but I’m, you know, talking about a lot of leverage. We want to win, and we will win. But I want to win as the Republican. I want to run as the Republican nominee.

Eventually, Trump made the pledge, which for most candidates is a pro-forma step to running.

The primaries were a running joke. At no time did Trump–despite pulling in millions of primary voters who had likely not participated in party politics in years, if ever–gain a majority of GOP votes in red states. He dominated blue states like New York and New Jersey.

Through Texas, Trump maxed out below 50 percent, where Reagan in 1980 was hitting 70 to 80 percent.

As the primaries went on, it didn’t get much better. Trump won with what number-crunchers call “an unconstrained plurality.” Read the astonishingly prophetic words of baseball stats guru Bill James as quoted in the Boston Globe, writing in 2001 about how, in 1999, Rafael Palmeiro won the Gold Glove for first base, despite playing only 28 games.

James called that voting structure “an open invitation to an eccentric outcome.” And then, the eye-popping conclusion: “If the United States were to use a system like this to elect the president, the absolutely certain result would be that, within a few elections, someone like David Duke, Donald Trump, or Warren Beatty would be elected president.”

Remember, James wrote that in 2001.

Instead of improving the voting system, the GOP has made it more eccentric by front-loading a short-lived proportional primary schedule designed to quickly winnow the field. Then comes the winner-take-all primaries to seal the deal. With a large enough field, as a black swan with instant name recognition, Trump couldn’t help but win.

Now, Priebus has given notice that the system will not be fixed–it will remain rigged to the likings of the Establishment (read: the same people who chose Donald Trump over Ted Cruz). This is being done to protect the Establishment’s cash flow and influence. It will, however, destroy the Republican Party.

Trump has no coattails. He has no wake for positive transformation. Trump is very much like Barack Obama to the Democrats, leaving Hillary Clinton the most unelectable Democrat in decades despite having the sitting president as an active surrogate. For the GOP, there is no positive outcome here.

In 2020, if Trump is president, I believe he will be vilified and booted from office with more gusto than the country mustered to evict Jimmy Carter in 1980, and nobody will be able to challenge him from his own party. If Trump loses, the GOP has announced that its best hope for a conservative revival is unwelcome in the party. And this is supposed to create unity?

There can be no more clear indication of how conservatives should expect to be treated by the RNC from here on out than Priebus’ threat. If this doesn’t motivate a third party movement for 2020, perhaps nothing will (and get used to single party Democratic rule). The GOP has just gone the way of the Whigs.