I have not publicly endorsed a presidential candidate in 44 years. But this year—the most important presidential election in my lifetime—I feel compelled to do so.

For decades I have advocated a completely pro-life agenda: pro-life and pro-poor; pro-family and pro–racial justice; pro–sexual integrity and pro-peacemaking and pro–creation care. This agenda is expressed in the National Association of Evangelicals’ public policy document “For the Health of the Nation.”

For decades, as I applied this agenda, I regularly concluded that Republican presidential candidates were better on issues like abortion, marriage and family, and religious freedom, while Democratic candidates were better on racial justice, economic justice, and the environment. So I have voted for both Republicans (George W. Bush) and Democrats (Barack Obama).

But 2016 is astonishingly different from other election years. Hillary Clinton is bad and good in the usual ways. But Donald Trump is not only bad in many of the usual ways—he is also bad in the ways in which I have usually preferred Republicans.

Trump’s recent pro-life stand is not credible. Historically he has supported abortion access, even to partial-birth abortion, and still supports Planned Parenthood, the country’s largest supplier of abortions.

Trump’s personal marriage record is horrendous. He humiliated his first wife by publicly flaunting an affair. He is now in his third marriage, while Clinton has remained with her husband in spite of his despicable behavior.

Trump’s call to ban all Muslims from immigrating to the United States was a fundamental violation of the constitutional ...

1