Parties need agendas. But President Trump has so thoroughly trashed his party's brand of free market loyalty, fiscal responsibility, and traditional values that one cannot help but wonder: What will the Grand Old Party stand for after Trump departs from the White House?

Here's my prediction: The GOP of the post-Trump future will intensify the culture wars against the liberal "enemy," and throw into the mix a regressive economic agenda that consists of nativist immigrant bashing and mercantilist America First-ism. Essentially, even without Trump, the GOP will fuel itself with Trumpism.

It would be easy to predict that Republicans would, after Trump, eschew Trumpism and instead return to austerity and traditionalism. After all, it's become a common criticism of the right that conservatives tend to forget about their commitment to fiscal responsibility when they control all the levers of government — and then rediscover it as soon as a Democrat becomes president. This has no doubt been the pattern in the past, and it would be reassuring if it were to be again in the future.

But that gives the GOP too much credit. The party spent the last decade erecting bulwarks against conservative sellouts that grow government and spend taxpayers into the poorhouse. Conservatives abolished earmarks, imposed budgetary sequesters, and insisted on the debt ceiling — only to crumble without resistance when Trump came along. Never before has a party fought so hard for something and then given it up so quickly. In one short year in office, President Trump has decimated conservatives' adherence to fiscal responsibility — without any audible protest from Republicans.

The two-year budget deal that he just signed exploded the sequester caps and threw in $300 billion more in defense programs that national security hawks wanted — and domestic programs that Democrats wanted, all without requiring any offsetting cuts. This is on top of $1.5 trillion in tax cuts that Trump obtained last year. No one believes the fairy tale that these cuts will pay for themselves through economic growth.

Obama-era budget deficits will balloon from around $500 billion to about $1 trillion annually. The nonpartisan Committee for a Responsible Federal Budget projects that by 2027 the U.S. debt will touch 105 percent of the GDP, a level not seen since the end of World War II. Even presidents fighting wars and slaying recessions haven't racked up deficits this big.

And what did the brave budget hawks do through all this?

Sen. Ted Cruz (R-Texas), the red-blooded Tea Party patriot who had used the debt ceiling under Barack Obama to engineer a government shutdown, voted for Trump's budget deal. Trump's budget director, Mick Mulvaney, a former member of the House Freedom Caucus who relentlessly attacked the profligacy of the left and the right during his time in Congress, pimped the Trump budget on Capitol Hill.

And then there was House Speaker Paul Ryan, Mr. Fiscal Responsibility himself. He has been an evangelist for reforming Medicare and Social Security lest the ginormous unfunded liabilities of these entitlement programs send America the way of Greece. But he too meekly bent his knee for Trump's spending extravaganza.

All of this goes far beyond the customary hypocrisy of politics. It is an epic self-repudiation that won't easily be reversed.

This means that the GOP agenda will face a vast emptiness. The only thing remaining to fill it will be Trump's brand of crass populism — as we are already seeing.

For better or worse, modern conservatism's defining ethos has been a protectiveness of American institutions — "standing athwart history yelling stop" — in the face of left-wing demands for social justice and radical reform. Yet ever more conservatives are swallowing the Flight 93 outlook that these institutions have become so irremediably corrupted by left-wing liberalism that the only way forward is by running them into the ground just like 9/11 passengers did to their hijacked plane. Hence, they stand by and watch — if not cheer — as Trump attacks the press as the enemy of the people and threatens to revoke the broadcasting licenses of networks whose coverage displeases him. Or openly castigates his own attorney general for recusing himself in the Russia investigation instead of loyally protecting him. Or goes after the FBI, formerly the cynosure of law-and-order conservatives, for focusing on Russia's election meddling rather than investigating his political opponents.

None of this is to suggest that Trump has no cause for complaint. But what's striking is that conservatives, of all people, have so little faith in the ability of America's impartial — if imperfect — institutions to ferret out some semblance of the truth and deliver some approximation of justice. Indeed, the healthy right-wing disgruntlement at an overweening bureaucracy and red tape has, under Trump, transmogrified into sinister conspiracy theories about a deep state controlled by liberals that is out to get American citizens. This is a new trope in the mainstream American political lexicon that didn't exist a year ago — and it isn't going away anytime soon.

But that is not the only aspect of Trumpism getting mainstreamed. So is xenophobia and protectionism. Conservatives' commitment to market competition and trade had tended to temper its parochial nationalism. Now, the entire conservative economic agenda is becoming an extension of its culture wars.

There is no better evidence of this than last week's Conservative Political Action Committee, a reliable barometer of grassroots sentiment. Two years ago, candidate Trump had to cancel his appearance at the gathering in the face of a planned walkout. This year Marion LePen, the leader of France's National Front, a rabidly nationalist party whose economic platform is to the left of Bernie Sanders and cultural platform to the right of alt-right leader Richard Spencer, was an honored guest. Her party is vehemently anti-trade and anti-immigration — and it favors universal government-run health care, forcing banks to lend money to small and mid-sized companies, and nationalizing roads.

But even as CPAC attendees rallied behind her ultra-nationalist message, they booed and hollered at Mona Charen, a highly respected conservative commentator. Indeed, Charen, who called out family values conservatives for ignoring Trump's serial-adultery and sexual predation allegations and inviting an ethno-statist like LePen, was escorted out by a security detail!

After such a rapid and complete implosion, conservatives won't be able to pivot back to their old principles. And who would believe them if they tried? Trump has beaten back his party's better angels and released its worst demons, which aren't likely to vanish anytime soon.