Donald Trump’s already notorious press conference on Wednesday morning managed to achieve a near perfect synthesis of Trumpism, by turns shocking in its transgressions and terrifying in what it portends. In between scolding a female reporter and calling Barack Obama, the man Trump hopes to replace, “the most ignorant president in our history,” Trump, astonishingly, invited Vladimir Putin’s Russia to “find” and distribute Hillary Clinton’s emails.

With his comments Wednesday, Trump has finally knocked over what was once a pillar of the Republican Party’s system of beliefs. For decades, the party has stood united behind the principle that the United States must have a strong national defense, take aggressive behavior by adversaries seriously, and confront threats with resolve. The primary enemy during most of this time was first the Soviet Union, and later a newly ambitious Russia, led by Vladimir Putin. In 2012, Mitt Romney labeled the country our top “geopolitical foe.”

Whatever you think of this posture—which too often involved smearing domestic opponents of a strong defense and those who registered even the smallest bit of sympathy for foreign enemies or rivals—it was at least consistently held and could be thoughtfully defended. Republican hawkishness united social conservatives and fiscal conservatives; it united the GOP base and the GOP establishment; and it defined the GOP in the minds of voters as the party of strong thinking about national defense.

Trump has already undermined the Republican Party’s supposed advantage on national security with his confusing and contradictory positions on foreign affairs: Sometimes he calls for a retreat from the world stage, other times he speaks darkly of secret plans to destroy ISIS, which he accuses Obama of treating with kid gloves. But by suggesting, last week, that the United States might withdraw from NATO, and on Wednesday inviting Russia to steal American data, Trump has shown just how hollow the Republican posture as defenders of our national security has become. That members of the Republican establishment can stand idly by as their nominee wields our foreign policy as a cudgel against his political enemies—and a tool to get himself elected—is the latest evidence that the party is ideologically bankrupt.

Imagine for a moment that the Democratic Party’s nominee announced that health care is not an issue that should concern the government and that people should be on their own—regardless of their needs—to pay their health bills. It’s the nearest equivalent I can think of to what Trump has just done by spitting on an idea so foundationally important to the Republican Party. Of course, no Democratic nominee would do such a thing. Whatever its myriad faults, the Democratic Party is not on the verge of falling victim to a demagogue; it is not, fundamentally, broken. The Republican Party is.

For people who never liked Republican foreign policy and think it is long overdue for a rethink, remember this: Trump isn’t repudiating GOP doctrine in a serious way. Instead, he is doing so by inviting Vladimir Putin to meddle in an American election and all but daring him to attack American allies by saying he wouldn’t necessarily abide by NATO’s promise to protect them. (Those who rightly criticize much American behavior during the Cold War would do well to remember that the collective security provided by NATO was one of the few indisputable achievements of that period.)

It’s of course possible that Republicans like John McCain and Marco Rubio will come out in the next few days, denounce Trump, and withdraw their support for him. It’s also possible that the moon landing was staged. The reason it is unlikely that GOP hawks will turn on Trump is the same reason they offered support to him in the first place: They are key members of a party that has decided to put short-term self-interest ahead of principle.

Read more Slate coverage of the 2016 campaign.