THERE are many lessons that conservatives need to learn from the rise of Donald Trump. There are elements of his message that the party should embrace. There are grievances among his voters that the Republican Party must address.

But for conservatives to support Trump himself, to assist in his election as president of the United States, would be a terrible mistake.

It would be a particularly stark mistake for conservatives who feel that the basic Reaganite vision that’s dominated their party for decades — a fusion of social conservatism, free-market economics, and a hawkish internationalism — still gets things mostly right.

In large ways and small, Trump has consistently arrayed himself against this vision. True, he paid lip service to certain Reaganite ideas during the primaries — claiming to be pro-life, promising a supply-side tax cut, pledging to appoint conservative judges. But the core of his message was protectionist and nativist, comfortable with an expansive welfare state, bored with religious conservatism, and dismissive of the commitments that constitute the post-Cold War Pax Americana. And Trump’s policy forays since clinching the nomination have only confirmed his post-Reagan orientation.