NASHVILLE — At least since Martin Luther nailed his theses to the church door in 1517, Christians have disagreed on what Jesus calls them to do in the name of faith. There are nearly 34,000 Christian denominations worldwide, a number that doesn’t account for American Christians — nearly one in six, according to a Gallup poll last summer — who belong to no denomination at all.

But as lively as Christian debate can be, the special Senate election in Alabama has exposed how closely conservative Christianity is now in lock step with the Republican Party. I grew up in Alabama, and I don’t doubt the sincerity of my fellow believers on the other side of the political aisle, but when faithful Christians vote for a man credibly accused of child molesting, something is terribly wrong with Christianity. (With white Christianity, that is: Black Christians overwhelmingly supported the Democratic candidate, Doug Jones.) Eighty percent of white born-again Christians voting in Alabama backed Roy Moore, and there is no skirting the damage they’ve done to their own moral standing.

The day of the election, the editor in chief of Christianity Today, Mark Galli, identified the biggest loser in Alabama: Christian faith itself. From now on, Mr. Galli wrote, “When it comes to either matters of life and death or personal commitments of the human heart, no one will believe a word we say, perhaps for a generation.”

Christianity presents a conundrum for evangelicals considering a monstrous political candidate who is also a Christian. The very foundation of our faith lies in the infinite mercy of a loving God, and it’s hard for an ordinary sinner to cast the first stone. Last year I asked an evangelical friend how she could bring herself to support a presidential candidate like Donald Trump, whose behavior is so at odds with her own. “He says he’s changed,” she said, “and I believe in God’s redemption. If I didn’t, how could I get out of bed in the morning?”