Where do we go from here? To a large swath of Americans and most of the rest of the world, American politics have careened out of control, lurching from a role model of sensible policy making and civil discourse to gridlock over even modest proposals with bipartisan buy-in, and to a presidential campaign with the kind of angry populist bluster, coarse language and sectarian division formerly associated with Peron-style banana republics.

On the policy front, the Republican Congress has made the unprecedented decision to portray a president with almost a year left in his term as not simply a “lame duck” but utterly bereft of any legitimacy to carry out the responsibilities of his office. Both House and Senate have declined to recognize the budget the president submitted in January, refusing even to hold the customary hearings with the head of the National Economic Council and the director of the Office of Management and Budget. And within an hour of the announcement of the sudden death of Supreme Court Justice Antonin Scalia, Senate Majority Leader Mitch McConnell made it clear that the Senate would not recognize any nominee put forward by Obama—no vetting, no hearing, not even the customary individual meetings with Judiciary Committee Republicans.

On the campaign front, the emergence of Donald Trump and Ted Cruz as the leaders of the Republican presidential pack—one a demagogic populist outsider who has never served in public office and had no role in the party, the other an extreme right-wing ideologue whose twin calling cards are engineering a government shutdown and going on the Senate floor and calling his own leader a liar—turned conventional presidential politics on its head, leaving a Republican political establishment reeling and a broader group of concerned Americans frightened about the future.

These developments are shocking and sobering but not entirely unexpected. Our 2012 book, It’s Even Worse Than It Looks: How the American Constitutional System Collided With the New Politics of Extremism asserted that the Republican Party had become radicalized, with unhappy consequences for its own future as a vibrant, competitive party and for the ability of the political system to solve problems facing the nation. In the new version, just out, we noted that the usual path for the GOP, selecting a presidential candidate from the ranks of the political establishment, was unlikely to happen this time. One of us wrote a column in The Atlantic in August suggesting the emergence of Trump and Cruz and the possibility of a contentious July convention in Cleveland.

Donald Trump’s emergence as the GOP frontrunner and likely nominee creates an existential crisis for the Republican Party, as the angry populism exploited and incited by Republican leaders in Congress to regain majority control turns inward to consume its host. The potential outcomes are bad for the party and its adherents—but even worse for the rest of America.

After his very good night Tuesday, including a huge victory in Florida, Trump could indeed wrap up the party nomination before July, or be so close to the magic 1,237 delegates that it would be impossible to deny him the nomination. One of the two major parties would then be led by a man noted for his divisive, taunting and dangerous language, his extreme proposals on immigration and trade, his lack of knowledge about even basic public policies—and a set of ideas, on Social Security, Medicare, health reform and Planned Parenthood at odds with the entire Republican Party platform and nearly all of its members of the House and Senate. No doubt, most of those members, along with the other presidential candidates and party nabobs, would dutifully get behind their nominee—the mantra is “Anyone would be better than Hillary Clinton.” But that would mean not only forfeiting a chance to broaden the party base beyond a core of working-class white voters, but also creating irresolvable dissonance between the standard bearer and the party hierarchy, even greater than that between Barry Goldwater and the then-moderate GOP establishment in 1964.

To be sure, American politics are different in many ways than they were in 1964. There are no more moderates; indeed, on some issues Goldwater would be considered on the left in today’s party. And politics have become much more partisan—there will not likely be any elections where a major party presidential candidate loses 45, much less 49 states, like in 1964, 1972 or 1984. Most states now are firmly red or blue. But a Trump candidacy would leave substantial numbers of Republicans feeling lost and abandoned, while also mobilizing Hispanic, Asian American and African American voters, potentially costing the GOP its precious majority in the Senate and threatening serious erosion of its majority in the House.

Some prominent Republicans are weighing other options to counter what they see as a hostile takeover of their party by Trump. There is talk of creating a third-party effort, led by a card-carrying conservative, who might serve to put the nail in the coffin of Trump’s presidential chances but might also gin up turnout in critical Senate states by Republicans otherwise demoralized by Trump. But starting that effort early enough to get on most key state ballots would mean a GOP effort to blow up the chances of their party’s own nominee, making likely a convention that would resemble Chicago in 1968. No wonder Cleveland has asked for riot gear for 2,000 in advance of the July gathering.

More likely is a late-developing effort to make the reviled Cruz the nominee. Republican leaders in Congress, the states, and the Republican National Committee could conspire to snatch the nomination away from Trump by changing the rules or trying to make a sizable number of pledged delegates for Trump defect on a first or second ballot. And even if there is no conspiracy, if Trump goes into the convention with, say, 1175 delegates, just short of the 1,237 to make a majority, and is still denied the nomination, there will be mayhem on the floor and in the streets of Cleveland, and very likely an effort by Trump to damage the GOP nominee’s chances in November, whether by running as an Independent in states where he can qualify, or mounting a major campaign among his voters and sympathizers to Just Say No.

We may shock you if we say that whatever the circumstances, if Trump does capture the Republican nomination and there is no significant third party or independent effort, he has a chance, however remote it looks now, to win. With America’s tribal politics, any nominee probably starts with a floor of 45 percent of the votes. What if there is serious economic turbulence or a Paris-style attack in the fall? Could enough voters in key states like Ohio and Michigan go to the strong man? It’s possible. And although a Trump presidency would be constrained by the elements of the American political system that have brought gridlock—separated powers, separate institutions, and centers of power—it would not be pretty.

Trump’s monumental ego would be blown up even more by a presidential victory, and his modus operandi in business and the nominating process—telling his subordinates to act with no questions asked, using bluster and intimidation to force others to bend to his will—would be reinforced. He has already threatened House Speaker Paul Ryan with consequences if Ryan does not go along with his desires and priorities. And Ryan, Senate Leader McConnell, and other key Republicans and Democrats would not go along with most of them. Would Trump move unilaterally with executive actions, going far beyond any previous president? The prospect of American leadership in the world under a President Trump is downright frightening. What happens when Mexico and China tell him where to put his demands that they pay for a wall and alter their currencies and trading habits? What if Trump early on faces the kind of international challenge George W. Bush had when China shot down an American plane and refused to give it up? Would Trump react as Bush did, with restraint by using diplomatic means? Would Trump try to use the resources of the executive branch, including the Secret Service, the military, the IRS and intelligence agencies, to force members of Congress, the press and other countries to comply? Perhaps not. But there could quickly be a crisis in governance that has not been seen in generations.

Many mainstream Republicans have comforted themselves by noting that Trump has no strong or fixed ideology, and as a lifelong dealmaker, is used to some give-and-take. Maybe they are right. But given that he has no understanding of policy or how policy is made, no ties at all to veterans of politics and government, and disdain for all those who have been inside and made those terrible deals, it would be a long, long time before he would or could recognize the reality of governing in a democracy.

These questions, and the most probable answers to them, are enough to make us look for property in Australia. But it remains true that the likelihood of a Trump presidency is slim. That brings us to the other grim reality of American politics, the continuing tribal conflict and division in Washington. If Republicans in Congress can’t help themselves from giving a collective middle finger to the outgoing president, how will they treat a new Democratic president? If Hillary Clinton wins—after the vast majority of Republicans in Congress endorse their presidential candidate by demonizing the alternative, and given the long history of contentiousness between the Clintons and Republicans in Congress—is there any way it can be better?

The answer is maybe, at least in a small way. A Trump loss might finally empower Republican leaders in Congress, including committee leaders who want to recapture their party and brand it as a problem-solving conservative party, to find areas to work with the new president, at least for a while before the permanent campaign and the midterm imperative take over again. If a President Clinton chooses early priorities wisely, she might be able to help a few over the finish line, in areas like infrastructure and tax reform. Despite the rhetoric of Republicans in Congress, many in the Senate have had very good personal and professional relationships with Clinton from her time there, and she showed a strong grasp of the legislative process when she was in the Senate. And Clinton would be able, through her appointments to executive and judicial positions, to shape a lot of policy, at least incrementally, outside the legislative arena.

But we have to be honest. The near-term future of politics and policy in America is a pretty grim one. Intimidated by the nihilist, nativist pressure from talk radio hosts and bloggers, Republican leaders in Congress are not all that likely to ignore their desires. That may mean continued stonewalling on a Supreme Court seat, leaving a 4-4 Court for a long time (though a Democratic Senate would likely do what it takes to confirm a Clinton nominee). A Trump loss—which he would surely blame on the enemy within—would not mean the demise of a Trump movement or the angry populism behind it, and the driving need by Republicans to recapture their party’s mojo in the midterm would probably have them fall back on the populist approach that worked in 2010 and 2014. So brace yourselves for a rocky road ahead, not just in 2016 but in 2017 and beyond.