Yet the support being given by many Republicans and white evangelicals to President Trump and now to Mr. Moore have caused me to rethink my identification with both groups. Not because my attachment to conservatism and Christianity has weakened, but rather the opposite. I consider Mr. Trump’s Republican Party to be a threat to conservatism, and I have concluded that the term evangelical — despite its rich history of proclaiming the “good news” of Christ to a broken world — has been so distorted that it is now undermining the Christian witness.

Just the other day I received a note from a friend of mine, a pastor, who told me he no longer uses the label “evangelical” to describe himself, even though he meets every element of its historical definition, “because the term is now so stained as to ruin my ability to be what evangelicalism was supposed to be.”

Another pastor who is a lifelong friend told me, “Evangelical is no longer a word we can use.” The reason, he explained, is that it’s become not a religious identification so much as a political one. A third person, who heads a Christian organization, told me the term evangelical “is now a tribal rather than a creedal description.” In October, the Princeton Evangelical Fellowship, a campus ministry for more than 80 years, changed its name to the Princeton Christian Fellowship. “We’re interested in being people who are defined by our faith and by our faith commitments and not by any sort of political agenda,” according to Bill Boyce, who has led the campus group for decades.

There are of course a great many honorable individuals in the Republican Party and the evangelical movement. Those who hold different views than I do lead exemplary lives. Yet I cannot help believing that the events of the past few years — and the past few weeks — have shown us that the Republican Party and the evangelical movement (or large parts of them, at least), have become what I once would have thought of as liberal caricatures.

Assume you were a person of the left and an atheist, and you decided to create a couple of people in a laboratory to discredit the Republican Party and white evangelical Christianity. You could hardly choose two more perfect men than Donald Trump and Roy Moore.

Both have been credibly accused of being sexual predators, sometimes admitting to bizarre behavior in their own words. Both have spun wild conspiracy theories, including the lie that Barack Obama was not born in America. Both have slandered the United States and lavished praise on Vladimir Putin, with Mr. Moore declaring that America today could be considered “the focus of evil in the modern world” and stating, in response to Mr. Putin’s anti-gay measures in Russia: “Well, maybe Putin is right. Maybe he’s more akin to me than I know.” Both have been involved with shady business dealings. Both have intentionally divided America along racial and religious lines. Both relish appealing to people’s worst instincts. Both create bitterness and acrimony in a nation desperately in need of grace and a healing touch.