Donald Trump is bad for America.

He is bad for the Republican Party. He is bad for the conservative movement. He is bad for the country he wants to lead. And while he promises to “make America great again,” we worry the effects of a Trump presidency - or even of a candidacy that lasts very long into the new year - will damage the fabric of this country in such a fashion that it might take years, maybe decades, to recover.

Most weeks, you read the two of us debating the latest issues. We have differing perspectives and differing stances. Those differences haven’t changed. But we are jointly so alarmed at Trump’s sustained position at or near the top of the primary season presidential polls that we feel compelled to join forces on this occasion and say: No. This must end.

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To be sure, we have differing reasons to arrive at the same conclusion.

For liberals, the problem with Trump is one of both tone and substance. Trump seems to have no rival deserving of respect, no enemy to approach diplomatically; instead he offers alpha male boastings about his superiority in all things and the inferiority of everybody else in, well, just about everything. It’s a great persona for a reality show. In a potential president, it is almost certainly disastrous. Unfortunately, his supporters seem to see this as a chief virtue.

Trump seems to reserve his greatest contempt for minorities - be they Latino immigrants, African-Americans or Muslim refugees. American citizens are understandably worried about a world in which their wages don’t go as far as they used to and in which terrorism lurks as a threat to them and their neighbors. History shows us that during such times, minorities are often made scapegoats - and Trump shows every sign of having learned precisely the wrong lessons from history. This isn’t just a matter of creating hurt feelings: It does the work of the Islamic State and al-Qaida for them. Trump, simply, exacerbates divisions where unity can be a prime strength - and safety - of the United States.

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Liberals would argue that Trump’s ascendancy is the natural culmination of the angry populist anti-liberal media institutions the right has built over the last 25 years - talk radio, Fox News and Breitbart.com among them - but we can’t help but notice that many conservative pundits and intellectuals also seem alarmed by Trumpism.

Conservatives - no, not simply “Republicans in name only” or other such hobgoblins - also have a problem with Trump’s tone and substance. Put simply, Trump isn’t a conservative at all.

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Until a short time ago, Trump advocated single-payer health care, abortion on demand, and a wealth tax that would make Vermont socialist Bernie Sanders envious. The real estate mogul remains an unapologetic supporter of government using eminent domain to take private property from one owner and give it to another in the name of “economic development.”

He claims to be pro-growth, but his policy proposals owe more to the liberal economist John Maynard Keynes than libertarian Milton Friedman or Reaganite Art Laffer.

Which speaks to a much larger problem Trump has created for Republicans: He is turning legitimate policy issues into radioactive wastelands, unsafe for public discussion.

From taking a second look at visa waivers and vetting refugees to holding China to account for unfair trade practices and cutting the corporate tax rate, Republicans will now spend as much time and energy distinguishing their proposals from Trump’s as they will simply making the argument.

Does the Republican Party establishment need a kick in the teeth? Yes. Every election cycle throughout the Obama era, Republicans have promised voters they have a plan to undo the excesses of the administration. And every time a new Congress comes into session, Republican leaders renege on their promises.

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Is the GOP too stupid to learn its lesson? Almost certainly. Republican voters are furious - so furious that many of them aren’t thinking straight. A large swath of conservative voters, even voters who don’t support Trump, wouldn’t mind seeing the current party establishment burned down. The GOP leadership does not appear to understand the gravity of the situation.

From time to time, a demagogue emerges who captures the imaginations of the people. Trump’s supporters tell us they like him because “he is his own man” and beholden to no patron or special interest. That’s fine as far as it goes. But don’t be surprised when Trump decides he isn’t beholden to the Constitution, checks and balances, or the American people.

Trump is, to use his favorite locution, a disaster - for Republicans and for the republic.

Ben Boychuk (bboychuk@city-journal.org) is associate editor of the Manhattan Institute’s City Journal. Joel Mathis (joelmmathis@gmail.com) is associate editor for Philadelphia Magazine.