I have been a Republican as long as I can remember. Joining the Grand Old Party seemed like a natural choice for someone like me who fled the Soviet Union as a boy and came to Los Angeles with his mother and grandmother in 1976. Refugees from communism, whether from Russia or Cuba, generally oppose socialism and embrace conservative political views.

My allegiance to the GOP was cemented during the 1980s, when I was in high school and college and Ronald Reagan was in the White House. For me, Reagan was what John F. Kennedy had been to an earlier generation: an inspirational figure who shaped my world view. Reagan had his faults, like JFK, but he was optimistic and gentlemanly. He was pro-free trade and pro-immigration. He believed in limited government at home and American leadership abroad.

That’s what I believed in, too — and that’s what I thought the Republican Party stood for. That’s why, despite my disagreements with social conservatives, I worked as a foreign policy adviser to John McCain in 2008, Mitt Romney in 2012 and Marco Rubio this year. All of those candidates, different as they were, recognizably represented Reagan Republicanism.

For the time being, at least, that Republican Party is dead. It was wounded by the Tea Party absolutists who insisted on political purity and rejected any compromise. Now it has been killed by Donald Trump.

Trump is an ignorant demagogue who traffics in racist and misogynistic slurs and crazy conspiracy theories. He champions protectionism and isolationism — the policies that brought us the Great Depression and World War II. He wants to undertake a police-state roundup of undocumented immigrants and to bar Muslims from coming to this country. He encourages his followers to assault protesters and threatens to sue or smear critics. He would abandon Japan and South Korea and break up the most successful alliance in history — NATO. But he has kind words for tyrants such as Vladimir Putin.

There has never been a major party nominee in U.S. history as unqualified for the presidency. The risk of Trump winning, however remote, represents the biggest national security threat that the United States faces today.

But if I’m not for Trump, who am I for?

Hillary Clinton is a centrist Democrat who is more hawkish than President Obama and far more principled and knowledgeable about foreign affairs than Trump, who is too unstable and erratic to be entrusted with the nuclear triad he has never heard of. Even in his prepared foreign policy speech he couldn’t pronounce “Tanzania.” For all her shortcomings (and there are many), Clinton would be far preferable to Trump.

But I am not prepared to join the party that she leads, because so much of it appears to be well to her left. Grass-roots Democrats thrilled this year to Bernie Sanders, a self-professed socialist who is almost as extreme in his own way as Trump is. I don’t “feel the Bern” and I can’t make common cause with those who do. Nor do I support Obama and his “lead from behind” foreign policy, which has created an opening for predators like Russia, Iran and the Islamic State — dangers that would only grow under a Trump presidency.

Perhaps a third party will arise as a vehicle for the 37 percent of conservatives who said in a recent poll that they have an unfavorable opinion of Trump. I would support it, because a third-party candidate could take away votes from Trump and make clear that he is not an authentic voice of conservatism. But third parties have never succeeded in the long term in our political system.

As it stands, I only know one thing for sure: I won’t vote for Trump. My hope is that he will lose by a landslide, and the Republican Party will come to its?senses, rejecting both his ugly, nativist populism and the extreme, holier-than-thou conservatism represented by Ted Cruz.

There is no shortage of Republican leaders today — the most prominent is U.S. House Speaker Paul Ryan — who represent Reaganesque conservatism. As far as I’m concerned, they are the real Republican Party, in exile. I only hope that they — and I — can return from the wilderness after November.

Max Boot is a senior fellow at the Council on Foreign Relations.