During a typical week in late May, Donald J. Trump, the presumptive Republican nominee for the U.S. presidency, grabbed headlines yet again. He declared a popular former president to be a “rapist,” flipped his position on one policy after another, bragged that his running mate could be “anyone” who supported him, and told the National Rifle Association that Hillary Clinton, the likely Democratic nominee, would “release violent criminals from jail.”

Perhaps most worrisome from a global perspective, just hours after an EgyptAir plane crashed into the Mediterranean, and long before any certain facts were known, Trump began stating his own conclusions about what had happened and denouncing American “weakness” in the face of terrorism.

Virtually all efforts to prevent Trump’s nomination have ended, and establishment Republicans are moving steadily to reconcile themselves with their party’s capture by an uncouth, narcissistic, unprepared and mercurial bully. “You’re better off riding the beast than trying to ignore it,” explained a former GOP Senate aide.

Many certainly did try to ignore it. No sooner had Trump announced last summer that he would seek the Republican nomination than pundits and political scientists started to find compelling reasons to dismiss his bid.

I was less certain, because I assessed Trump’s emergence and prospects against the backdrop of my ongoing research on the U.S. political right. Back in 2010 and 2011, Vanessa Williamson and I studied the popular and elite forces that gave rise to the Tea Party and helped pull the Republican Party further rightward.

More recently, I have worked with Alexander Hertel-Fernandez and other researchers to decipher shifts in organized conservative politics. Such shifts include the rising influence of Charles and David Koch, billionaire brothers whose network of think tanks and advocacy organizations has encouraged an ultra-free-market economic agenda among Republican candidates and officeholders at state and national levels. Pulled in different directions by plutocratic funders and angry nativist populists, the GOP became ripe for a Trump-style hostile takeover.

Starting early in Barack Obama’s presidency, as Tea Party populists took center stage, Trump became popular because he championed efforts to delegitimize America’s first black president. An April 2011 opinion poll found Trump leading all GOP presidential contenders for 2012, with especially strong backing from Republicans who firmly believed that Obama, as Trump insisted, had not been born in the United States, as the U.S. Constitution requires.

Trump did not run in 2012, but grassroots Tea Partiers were already focused on illegal immigration and hatred of Obama. Over the course of that year’s presidential primaries, at least half of GOP voters repeatedly tried to find an alternative to the eventual Republican nominee, Mitt Romney, but could not coalesce around a viable contender.

GOP leaders’ failure to stop Obama in 2012 and roll back his initiatives intensified populist Republicans’ anger at their own party. By the beginning of the 2016 presidential cycle, it seemed clear that many would seek a unifying “antiestablishment” candidate.

In an effort to capture this voter rebellion, Sen. Ted Cruz of Texas repeatedly bucked GOP congressional leaders. But the media-savvy Trump blindsided Cruz and all other contenders. Starting in the summer of 2015, he embraced extremist rhetoric appealing to nativism, Islamophobia and anger at GOP elites. Media outlets provided as much as $2 billion worth of free coverage, helping him grab and hold leads in polls and most primaries.

Trump’s core supporters are wrongly thought to be displaced and economically insecure blue-collar workers. In fact, his voters’ average annual income, about $72,000, is well above the U.S. median of $56,000. His supporters resemble the Tea Partiers: overwhelmingly older, male, middle class and white. They report anxieties about the economy -- as most Republicans do -- but what sets them apart is disbelief in Obama’s legitimacy, anger about immigration and resentment over America’s supposed national decline.

Trump supporters are more likely than other Republicans to hold negative stereotypes about blacks and Latinos. And it seems quite likely that, as we found for Tea Partiers in 2011, Trump backers approve of social welfare benefits that go to “real Americans” like themselves, while opposing public spending on minorities and low-income people.

Trump’s agenda thus resembles that of many European populist parties: a mix of anti-immigrant toughness, economic patriotism and social benefits for native-born citizens. But no major U.S. party has offered such a program, and even now GOP leaders and major funders, having moved the party further toward the free-market right during the Obama years, oppose it. In the U.S. Congress and state legislatures, Republicans hew to generally unpopular extreme positions -- tax cuts for the rich, evisceration of business regulations, lower social spending and curbs on union activities.

But, arguably, the GOP’s ultra-free-market extremism has backfired. When virtually all GOP contenders for 2016 signed on to that agenda, Trump exploited an opening for “America First” nativism and protectionism. In Trump’s disparagement of Latino immigrants, independent women and “uppity” minorities, his base hears a promise to “make America great again” by reasserting white male hegemony.

None of this is surprising. For years, GOP elites have played with fire by stoking popular nativism and racial fears to mobilize older white voters. With U.S. conservative media putting out a steady stream of racial innuendo, the GOP’s discourse was thoroughly debased well before candidate Trump, himself a media player, came along.

Could Trump actually win? Elected GOP officeholders, afraid to buck voter sentiment, are starting to declare their support. While some wealthy donors are redirecting their money to congressional and state-level candidates, many others have jumped on board -- and others will, too, to the degree that Trump seems able to beat Clinton.

In any two-party system as polarized and closely balanced as the current U.S. electoral system, a single crisis, such as a terrorist attack, could tip the balance. GOP politicians, funders and advocacy group leaders are now trying to convince themselves that Trump, in the White House, could be managed to implement the Republican agenda. A pivotal Supreme Court nomination is at stake, and Speaker of the House Paul Ryan has a government-slashing budget ready for a Republican president to sign.

Ryan, who has not yet officially endorsed Trump, will come under growing pressure to do so. The Republicans will ride the beast they created -- and hope that it does not consume them.

By Theda Skocpol

Theda Skocpol, professor of government and sociology at Harvard University, is the coauthor of “The Tea Party and the Remaking of American Conservatism.” -- Ed.

(Project Syndicate)