It was Oct. 27, 1964, and Barry Goldwater’s floundering presidential campaign needed to turn the tide. They turned to B-list actor and former Democrat named Ronald Reagan, giving him half an hour for a nationally televised address. The Reagan Revolution began that night. His speech “A Time for Choosing” would be too little, too late for Goldwater. But his central premise — that America faced a reckoning, that we could “preserve for our children this, the last best hope of man on Earth, or … sentence them to take the last step into a thousand years of darkness” — propelled him to the White House 16 years later. Today, facing an increasingly rowdy chorus of conspiracy theorists and provocateurs, Reagan’s party must answer a similar existential question. It is a time for choosing.

In the months since Joe Biden won the presidency, the GOP has descended into an all-out Civil War. A growing number of Republican elected officials have declared assault on the truth, amplifying patently false claims about a stolen election and cozying up to reprehensible conspiracy theorists. They are perhaps best represented by newly elected Rep. Marjorie Taylor Greene, a certifiable lunatic who was recently a proud member of QAnon and who has been receptive to the notion that 9/11 did not actually happen. Opposing this “Conspiracy Caucus” is the group broadly defined as “the establishment,” led by Rep. Liz Cheney in the House and Senate Minority Leader Mitch McConnell. This group rejected the “stolen election” fiction, and they were unequivocal in their condemnation of former President Trump’s actions on and after Jan. 6.

The Republican Party cannot be the long-term home for both of these groups. Conservatives believe in the enduring strength and majesty of our founding institutions; the conspiracists are content to burn them down if it means they can send out another fundraising email. The establishment seeks to secure meaningful conservative policy victories; the holy grail for the grifters is “owning the libs.” The GOP as it stands today is a house divided, and history’s greatest Republican reminded us that such a house cannot stand.

But the conspiracists will not go down without a fight. They will be well funded, powered by their army of small-dollar donors. The fragmenting of our political media and the “bubble” effect of social media will make it easier for their lies to go unchecked. They will be amplified and supported by Donald Trump, still a powerful figure within the Party.

So how does the Establishment go about reclaiming its Party? First, leadership matters. Republican leaders must make it clear that they condemn the statements and actions of those like Rep. Greene, and they must send unambiguous signals to the rank-and-file that they should do so as well. They must be active in 2022 GOP primaries, deploying their resources in defense of principled conservatives who have come under fire for living in the world of reality and going on the offensive against those who live in the world of fiction. In short, the Republican Party must act like a Party, putting its long-term survival ahead of immediate political expediency. But ultimately, the decision rests with Republican voters. Politicians respond to incentives, and right now, they see an incentive toward tolerating (or even leaning into) the more odious elements of the American right. It is when GOP primary voters no longer tolerate this nonsense that it will stop. It is up to them whether the GOP remains the last best hope of American conservatism or takes the step into an era of even deeper darkness. It’s time to choose.