Jeff Greenfield is a five-time Emmy-winning network television analyst and author.

Donald Trump may have eased some Republican fears Tuesday night when he declared his intention to stay inside the party. But if their angst has been temporarily eased at the prospect of what he would do if he loses, they still face a far more troubling, and increasingly plausible, question.

What happens to the party if he wins?


With Trump as its standard-bearer, the GOP would suddenly be asked to rally around a candidate who has been called by his once and former primary foes “a cancer on conservatism,” “unhinged,” “a drunk driver … helping the enemy.” A prominent conservative national security expert, Max Boot, has flatly labeled him “a fascist.” And the rhetoric is even stronger in private conversations I’ve had recently with Republicans of moderate and conservative stripes.

This is not the usual rhetoric of intraparty battles, the kind of thing that gets resolved in handshakes under the convention banners. These are stake-in-the-ground positions, strongly suggesting that a Trump nomination would create a fissure within the party as deep and indivisible as any in American political history, driven both by ideology and by questions of personal character.

Indeed, it would be a fissure so deep that, if the operatives I talked with are right, Trump running as a Republican could well face a third-party run—from the Republicans themselves.

That threat, in turn, would leave Republican candidates, contributors and foot soldiers with painful choices. A look at the political landscape, the election rules and the history of intraparty insurgencies suggests that it could turn 2016, a year that offered Republicans a reasonable chance to win the White House and with it total control of the national political apparatus, into a disaster.

***

With Trump as the nominee, the Republican Party would face a threat to unity on several fronts. His victory would represent a triumph of an insurgent movement, or impulse, within the party. Historically speaking, this is exactly the kind of intraparty victory that guarantees political civil war.

The most striking examples of party fissure in American politics have come when a party broke with a long pattern of accommodating different factions and moved decisively toward one side. It has happened with the Democrats twice, both over civil rights. The party had long embraced the cause of civil rights in the North while welcoming segregationists—and white supremacists—from across the South. In 1948, the party’s embrace of a stronger civil rights plank led Southern delegations to walk out of the convention. That year, South Carolina Governor Strom Thurmond led a National States Rights Democratic Party—the “Dixiecrats”—that won four Southern states. Had President Harry Truman not (barely) defeated Tom Dewey in Ohio and California, the Electoral College would have been deadlocked—and the choice thrown into the House of Representatives, with Southern segregationists holding the balance of power. Twenty years later, Alabama Governor George Wallace led a similar anti-civil-rights third party movement that won five Southern states. A relatively small shift of voters in California would have deadlocked that election and thrown it to the House of Representatives.

In two other cases, a dramatic shift in intraparty power led to significant defections on the losing side. In 1964, when Republican conservatives succeeded in nominating a divisive champion of their cause in Barry Goldwater, liberal Republicans (there were such things back then) like New York Governor Nelson Rockefeller, Michigan Governor George Romney and others refused to endorse the nominee. More shockingly, the New York Herald-Tribune, the semi-official voice of the GOP establishment, endorsed Lyndon Johnson—the first Democrat it had supported, ever. With his party split, Goldwater went down in flames. Eight years later, when a deeply divided Democratic Party nominated anti-war hero George McGovern, George Meany led the AFL-CIO to a position of neutrality between McGovern and Richard Nixon—the first time labor had refused to back a Democrat for president. Prominent Democrats like former Texas Governor John Connally openly backed Nixon, while countless others, disempowered by the emergence of “new Democrats,” simply sat on their hands. The divided Democrats lost in a landslide.

Would a Trump nomination be another example of such a power shift? Yes, although not a shift in an ideological sense. It would represent a more radical kind of shift, with power moving from party officials and office-holders to deeply alienated voters and to their media tribunes. (Rush Limbaugh, Sean Hannity, Mark Levin, Ann Coulter and Laura Ingraham have not exactly endorsed Trump, but they have been vocal in defending him and in assailing those who have branded Trump unacceptable.) It would undermine the thesis of a highly influential book, “The Party Decides,” which argues that the preferences of party insiders is still critical to the outcome of a nomination contest. This possibility, in turn, has provoked strong feelings about Trump from some “old school” Republicans. Says one self-described “structural, sycophantic Republican” who has been involved at high levels of GOP campaigns for decades: “Hillary would be bad for the country—he’d be worse.”

***

A battle over ideology or influence, however, explains only one kind of defection from party ranks. The other—one that would hold particular peril for Trump-as-Republican-nominee—arises from a belief that a chosen candidate is simply unfit, by character or temperament, to hold office. And on at least one occasion, a prominent politician sacrificed his electoral chances out of that belief.

In 1986, former Senator Adlai Stevenson III had every reason to believe he would be following his father's footsteps into the Illinois governor’s mansion. Four years earlier, the Democrat had lost a race for that office by fewer than 5,000 highly disputed votes. But in 1986, his easy primary win in March was overshadowed by what happened elsewhere on the ballot: Two followers of Lyndon LaRouche, a cultish, conspiracy-minded demagogue, won the Democratic nominations for lieutenant governor and secretary of state. Stevenson was so horrified by the thought of placing LaRouche’s acolytes in positions of political power that he bolted the party line, running instead as an independent. He lost decisively. (Sen. Alan Dixon, who remained on the Democratic line, easily won reelection.)

Republicans faced a similar issue in 1991, when former Klansman David Duke made it into the gubernatorial runoff in Louisiana. While he proclaimed himself a Republican, he was roundly rejected by the party at every level—the outgoing GOP governor endorsed former Governor Edwin Edwards—and Duke lost overwhelmingly to Edwards. (It’s a campaign best remembered for the bumper sticker touting the ethically challenged Edwards: “Vote for the crook—it’s important.”)

It’s this example that perhaps offers the best parallel to what Trump would face as the nominee. If you want to see the most sulfurous assaults on Trump, don’t look to the editorial pages of the New York Times or the comments of MSNBC personalities; look instead to the most prominent media voices in the conservative world: National Review, The Weekly Standard, Commentary and the columns of George Will and others. In part, they deplore his deviations from the conservative canon; deviations that former Reagan aide and onetime FCC Chairman Dennis Patrick summarizes this way: “Many of my colleagues from the Reagan administration would have a hard time pulling the lever for Trump. We weren’t just Republicans, we were conservatives. It is very difficult to square any principled theory of conservative governance with much of what Trump says."

But it’s more, much more than policy that has stirred the ire on the right: It’s the vulgarity, the fusion of ignorance and arrogance, the narcissism, the dissembling on matters great and small. The composite portrait of Trump painted by these outlets—leavened only by a grudging acknowledgment that he’s touched on legitimate concerns about immigration and terror—makes the idea of handing over the nuclear codes to Trump unsettling. And it makes the idea of embracing him as the alternative to Hillary Clinton somewhere between a reach and a lunge.

***

What a Trump nomination represents, then, is a victory that leaves significant slices of the party unwilling or unable to accept the outcome. Whether he’s seen as an ideological heretic for his views on trade, taxes and government power or as a demagogue whose clownish bluster and casual bigotry make him temperamentally unfit for office, the odds on massive defections are very high.

But what kind of defections? Based on the folks I’ve talked with, it could take different forms. One is a simple, quiet step away from any work on behalf of the top of the ticket. That’s what the self-described “structural, sycophantic Republican”—will do. While he fervently hopes Trump will meet the fate of past front-runners like [Rudy] Giuliani and [Newt] Gingrich, he says that in the event of Trump’s victory, “I would put all my heart, soul and energy into saving the Senate. I’d work to turn out votes so that [Kelly] Ayotte and [Pat] Toomey and [Ron] Johnson survive. In the end, every Republican, every conservative, knows what a disaster it would be to have Clinton as president. So the key is to make sure the checks and balances were in place.”

Others, however, can envision much more radical outcomes. Dan Schnur spent a lifetime in the vineyards of the Republican Party, working in the Reagan and Bush presidential campaigns and serving as communications director for the California Republican Party. He’s now an independent and heads the Unruh Institute of Politics at USC. He argues “a Trump nomination would virtually guarantee a third-party campaign from a more traditional Republican candidate.”

Why a Republican? The short answer is to save the party over the long term. “It's impossible to conceive that Republican leaders would simply forfeit their party to him,” he says. “Even without the formal party apparatus, they'd need to fly their flag behind an alternative, if only to keep the GOP brand somewhat viable for the future. Otherwise, it would be toxic for a long, long time.”

Romney strategist Stu Stevens, who still believes Trump will fade—indeed, that “he will not win a single primary”—nonetheless agrees that a Trump nomination would trigger a “very strong third-party effort.” And Rob Stutzman, another veteran of California Republican politics—he helped spearhead the 2003 recall that put Arnold Schwarzenegger in the Governor’s Mansion—foresees a third party emerging, both as a safe harbor for disaffected GOP voters and to help other Republican candidates.

“I think a third candidate would be very likely on many state ballots,” he says. “First of all, I think most GOP voters would want an alternative to vote for out of conscience. But Trump would also be devastating to the party and other GOP candidates. A solid conservative third candidate would give options to senators like Ayotte, Johnson and [Mark] Kirk to run with someone else and still be opposed to Hillary. In fact, I think it’s plausible such a candidate could beat Trump in many states.”

Any candidate attempting a third-party bid would confront serious obstacles, such as getting on state ballots late in the election calendar. As for down-ballot campaigns, most state laws prohibit candidates from running on multiple lines; so a Senate or congressional candidate who wanted to avoid association with Trump would have to abandon the GOP line to re-run with an independent presidential contender. The Stevenson example shows that leaving a major party line is fraught with peril—although the write-in triumph of Alaska Sen. Lisa Murkowski in 2010 suggests that it can sometimes succeed.

The very fact that serious political thinkers are contemplating such a possibility demonstrates that when Republicans look at the perils posed by a third-party bid from Donald Trump, they may be looking in the wrong direction. It’s not Trump the Defector that could trigger the biggest threat to the party, but Trump the Nominee.