On Monday, the John Kasich campaign released a remarkable video in which one of the Ohio governor’s supporters, Colonel Tom Moe, a Vietnam veteran and former POW, speaks against Donald Trump by paraphrasing Martin Niemoller’s famous “First they came” speech about the dangers of apathy in the face of Nazism. “You might not care if Donald Trump says Muslims must register with their government because you are not one,” Moe says with Midwestern calm. “And you might not care if Donald Trump says he’s going to round up all the Hispanic immigrants, because you are not one. And you might not care if Donald Trump says it is okay to rough up black protesters, because you are not one. And you might not care if Donald Trump wants to suppress journalists, because you are not one. But think about this: If he keeps going, and he actually becomes president, he might just get around to you, and you better hope there is someone left to help you.”

With its implicit linkage of Trumpism with fascism, Moe’s speech puts into stark relief the question of what happens if Trump “actually becomes president.” It also poses a dilemma for Kasich himself. During the first Republican debate, Kasich and all the other candidates were asked if they would promise to “support to the eventual nominee of the Republican Party and pledge to not run an independent campaign against that person.” Aside from Trump, they all said yes. Which means that Kasich—along with Jeb Bush, Marco Rubio, Chris Christie, Carly Fiorina, and the rest of the field—are committed to backing Trump if he is their party’s nominee. 

Although he continues to dominate the polls, the possibility of Trump triumphant still seems improbable. His long habit of making racist comments has only intensified in recent days, when he’s falsely claimed that thousands of Arab Americans in Jersey City cheered on the 9/11 attacks and re-tweeted bogus statistics about the black crime rate that originated from an avowed admirer of Adolf Hitler. He has virtually no institutional support in the party, is doing only cursory fundraising, and remains stingy about spending his own money, preferring to ride on the ample free publicity he receives. Trump is clearly betting that his strong polling performances will translate into actual votes. 

His gamble could pay off. And then the GOP will face a major dilemma, since the other candidates and party establishment will have to support a nominee they despise, and likely think is unfit for office. Trump has insulted almost all the other candidates in the most vicious ways imaginable, making derogatory comments about Bush’s energy level and marriage to a Mexican American, Rubio’s ethnicity, Fiorina’s physical appearance, and Ben Carson’s supposed similarities to child molesters, among other bon mots.

The Republican Party faces a nightmare scenario with Trump as its nominee, with two possible outcomes—both of which are unappetizing. The more likely possibility is that Trump could so offend the general public that the GOP would get a historic electoral drubbing to rival the 1964 defeat of Barry Goldwater, who carried only a handful of states and handed over super-majorities to Democrats in Congress and the Senate. Democrats are highly unlikely to win such super-majorities in 2016, but with the Republican ticket headed by a loudmouth bigot they could certainly pick up seats in the House and re-take the Senate. 

But the other possible outcome is even worse for the GOP: Trump could win the presidency. A recent Washington Post article about panic within the Republican establishment made clear that there are leading figures in the party who are terrified at the prospect of a Trump presidency. “We’re potentially careening down this road of nominating somebody who frankly isn’t fit to be president in terms of the basic ability and temperament to do the job,” one GOP strategist told the Post. “It’s not just that it could be somebody Hillary could destroy electorally, but what if Hillary hits a banana peel and this person becomes president?” Here is a Republican strategist having nightmares about a Republican candidate winning the White House.

So how would Republicans deal with Trump as their candidate? As it happens, the 1964 election offers a likely guide to how the GOP could be riven apart and where that could take the party—and American politics. 

Barry Goldwater’s nomination tore the party in half because he was the avatar of a wider conservative insurgency that displaced the moderate Republicanism of President Eisenhower’s crowd. For the moderates, Goldwater was a frightening figure not only because he adopted extreme positions (opposition to the Civil Rights Act, an unwillingness to disavow the conspiracy-obsessed John Birch Society), but also for his habit of making reckless remarks, like suggesting the Pentagon “lob one into the men’s room at the Kremlin.”

Before Goldwater got the nomination, GOP notables and his rivals had attacked him in the fiercest possible terms. Richard Nixon, who was in between presidential runs that year, described Goldwater’s opposition to civil rights as a “tragedy.” New York Governor Nelson Rockefeller, who was a candidate, said, “Barry Goldwater’s positions can spell disaster for the party and the country.” Pennsylvania Governor William Scranton, another presidential hopeful, called Goldwaterism a “crazy quilt collection of absurd and dangerous propositions.”

The hostilities played out on national television during the convention in which Goldwater was selected in San Francisco. Rockefeller and Scranton tried to exert a moderating influence on the platform, only to be met with heckling and catcalls. Eisenhower said the ruckus of the convention was “unpardonable—and a complete negation of the spirit of democracy. I was bitterly ashamed.” The former president also said that during the convention his young niece had been “molested” by Goldwater-supporting hooligans. The disarray of that convention anticipated some of the rowdiness of Trump events, as in the recent roughing up of a black protester in Birmingham, Alabama, which Trump himself egged on and justified.

Goldwater’s campaign had a profound impact on the racial composition of the Republican coalition. As historian Geoffrey Kabaservice notes in his 2012 book Rule and Ruin: The Downfall of Moderation and the Destruction of the Republican Party, “Many progressives and moderate Republicans did not want to participate in the Goldwater campaign in any way, shape, or form. The party’s African-American supporters were a special case in point. … African-Americans comprised only one percent of delegates and alternatives at the convention, a record low. Even so, there were some ugly incidents when Southern whites baited the blacks with insults and racial epithets and, in one case, deliberately burned a black delegate’s suit jacket with cigarettes.” Baseball star Jackie Robinson, then the most famous black Republican, said, “I now believe I know how it felt to be a Jew in Hitler’s Germany.” 

Robinson also suggested that any black delegate who supported Goldwater would be “through in his hometown.”

Goldwater’s hard-right stance on civil rights alienated African American voters from the Republican Party in an enduring way. In 1956, 39 percent of the African American vote went to the Republicans, in 1960 it was 32 percent, and in 1964 it plummeted to 6 percent. Since Goldwater, the Republican presidential candidate has never gotten more than 15 percent of the black vote, and usually far less. A Trump nomination could have a similar effect by alienating Latinos, and perhaps all non-whites, thereby making the Republican Party even more monochromatic going forward than it already is. 

As might also happen with Trump, even Republicans who publicly supported Goldwater privately acknowledged he was unfit for the position. In 1964, after Goldwater had won the nomination, Time magazine correspondent Richard Clurman asked National Review editor William F. Buckley, “How does someone of your intellectual gifts become a prime supporter of a very pleasant, but obviously such a limited, man?” Buckley replied by saying, “Barry Goldwater is a man of tremendously decent instincts, and with a banal but important understanding of the Constitution and what it means in American life.” Clurman pressed the point and asked what would happen if Goldwater were elected president. “That might be a serious problem,” Buckley joked. 

Buckley’s quip was entertaining, but it gets to the heart of a dilemma that the more intelligent professional Republicans and their journalistic supporters have to face: If Trump is the candidate, do they put party before country and work to elect a man they know is completely unfit for the office? Or do they break ranks and endanger their standing in the party? 

These two paths also faced Republican politicians in 1964. Rockefeller and Scranton gave only nominal support to Goldwater, but made it clear they didn’t want him to win. Nixon had no more private regard for Goldwater, but he acted as a party loyalist, placing Goldwater in nomination at the convention and campaigning hard. Rockefeller and Scranton faced blighted political futures after 1964, unforgiven by the conservative wing of the party. Nixon’s loyalty was remembered and rewarded when he became the party nominee in 1968. Rubio and Ted Cruz, who’ll be hoping for a presidential future even if they lose this year, will surely be taking note.

Will Republicans walk in the footsteps of Rockefeller and Scranton, turning their backs on Trump? Or will Nixonian expediency rule the day? One clue lies in the words of Senator John McCain, whose war record Trump has insulted. McCain has said that he would support whoever the Republican nominee is, and vote for Trump over Hillary Clinton. The senator ran in 2008 under the slogan “Country First.” Given his current position, he should modify that to “Party First.” 

The lessons of 1964 are clear: Even a losing and divisive candidate changes the orientation of the party. After Goldwater, Nixon triumphed because he was able to co-opt many conservative movement pet causes and make them more palatable to mainstream Americans. Nixon’s Southern Strategy and use of racist dog whistles was a successful re-packaging of Goldwaterism. If Trump is the Republican nominee in 2016, he’ll transform the party even if he loses. A Trumpized Republican Party, much more xenophobic than even now, will be the new norm. And the stage will be set for a new Nixon—most likely Cruz or Rubio—to become the more polished Trump and win the White House.