Everything that’s wrong with America is Barack Obama’s fault. That’s what Republican politicians have told themselves and the public for eight years. It began before Obama took office, when Republicans blamed him for a recession that started on their watch. Now they’re blaming Obama for the rise of their own presidential front-runner, Donald Trump.

The delusion that Obama caused Trump has been building since last year. This week, it reached the last bastion of rationality on the right: New York Times columnist Ross Douthat. Douthat has a long track record of fairness and good sense. When the madness infects even him, it’s time to clear the air. No, Obama didn’t cause Trump. What caused Trump was the GOP’s decision to negate Obama in every way, and thereby become the party of Trump.

As president, Obama was never a radical leftist. He extended the drone program, the Iran sanctions, and the bailout-recovery policies of George W. Bush. He proposed to cut the national debt through a higher ratio of spending cuts to tax increases than even Bush’s father had accepted and Republican voters preferred. Obama embraced the Heritage Foundation’s idea of imposing personal responsibility for health care costs through an individual mandate to buy insurance. He decimated al-Qaida’s leadership, built up troop strength in Afghanistan, and killed Osama bin Laden.

Nevertheless, Republicans opposed Obama at every turn. Whatever he embraced, they rejected. They refused to compromise on health care or offer a realistic alternative. They staged dozens of votes to repeal the new health-insurance law in its entirety. They forced a federal shutdown to protest the law. They took the nation’s credit rating hostage in a debt-ceiling showdown. They urged Iran to reject a nuclear nonproliferation agreement with the United States.

In 2012, Republicans lost the Hispanic vote and the presidential election. An internal autopsy report on this defeat, commissioned by the Republican National Committee, concluded: “We must embrace and champion comprehensive immigration reform.” Instead, in 2013 and 2014, House Republicans killed immigration reform. Today, Sen. Ted Cruz hounds Sen. Marco Rubio for having consorted with Obama to support the bill, and Rubio dutifully renounces it.

If Obama had been a leftist, the GOP’s policy of negating him on every issue might have positioned Republicans in the mainstream. Instead, because Obama was a moderate, the GOP’s negation strategy pushed it toward the fringe. Obama was for fiscal responsibility and compromise, so Republicans were for absolutism and drama, risking a federal shutdown and a credit default. Obama was for respecting the Supreme Court, so the GOP was for defying judicial orders. Obama was for using sanctions to pressure Iran into a nuclear deal, so Republicans were for scrapping the deal and daring Iran to provoke a war. Obama, like Bush, was for drawing a clear distinction between terrorists and Muslims. So Republicans were for blurring that distinction.

In Trump, Republican voters have found their anti-Obama. Trump spurns not just political correctness, but correctness of any kind. He lies about Muslims and 9/11, insults women and people with disabilities, accuses a judge of bias for being Hispanic, and hurls profanities. Trump validates the maxim that in presidential primaries, the opposition party tends to choose a candidate who differs temperamentally from the incumbent. Obama is an adult. Therefore, Republicans are nominating a child.

The GOP’s predicament isn’t just that Trump is leading the fight for the nomination. It’s that his only viable opponents are men who claim he’s not conservative enough. In rallies and interviews, Cruz and Rubio call Trump soft on immigration and gun control. They denounce him for praising Planned Parenthood’s work against cervical cancer and breast cancer. They’re outraged that Trump has said he supports government-funded health care to prevent sick people from dying in the streets—as though there were some way other than government-funded health care to guarantee that sick people don’t die in the streets.

How did the GOP end up in this madness? By twisting itself to thwart and vilify Obama. Cruz paints the president as a traitor “who doesn’t believe in the mission of our military and who undermines them at every step.” Rubio, incensed at Obama’s inclusive language, repeatedly excoriates him for “talking about discrimination against Muslims.” Both senators pledge to shred the Iran agreement on their first day in office—apparently out of spite, since renouncing the agreement would free Iran of its nonproliferation commitments without recovering the money that was relinquished in sanctions relief.

What has Obama done to provoke this psychosis? Douthat says he abused executive authority. But that’s circular: Obama resorted to executive action when Republicans blocked the normal channels of government. The GOP’s sabotage began the moment Obama took office, and it exceeds anything done to previous presidents. I’m hard-pressed to come up with an innocent explanation.

The immigration debate illustrates the madness. Four years ago, Republicans campaigned against illegal immigration but emphasized their support for legal immigration. Now that distinction is all but lost. Cruz, who has renounced his prior advocacy of visas for foreign workers, complained at a rally in Oklahoma on Sunday that “the Democrats support immigration.” Even Douthat, in his column on Obama, writes nostalgically, “It was possible to be a culturally conservative skeptic of mass immigration in the Democratic Party of Bill Clinton. Not so anymore.” Note the absence of the word illegal.

So, yes, Obama led to Trump. But that’s only because the Republican Party decided to be what Obama wasn’t. And what Obama wasn’t—insecure, bitter, vindictive, xenophobic, sectarian—is what the GOP, in the era of Trump, has become.

Read more Slate coverage of the 2016 campaign.