Rep. Tim Murphy (R-Pa.) speaks on Capitol Hill in Washington on March 26, 2015. (Andrew Harnik/Associated Press)

THE HOUSE on Tuesday voted to ban abortions of fetuses that have passed 20 weeks of gestation, sending to the Senate a bill purportedly about protecting fetuses capable of feeling pain. Among the reasons for skepticism: The American Congress of Obstetricians and Gynecologists says that fetuses cannot feel pain at 20 weeks, and the Senate almost certainly will not pass the bill. The House would have better spent its legislative time if it had renamed a post office somewhere. No matter: Republicans need money and passion from antiabortion groups, who insisted on moving the bill, and it passed by a 237-to-189 vote.

One of the bill’s co-sponsors was Rep. Tim Murphy (R-Pa.). On the same day Mr. Murphy was voting for the bill, the Pittsburgh Post-Gazette published text messages that appear to show the congressman and a woman he had a relationship with discussing how he pressured her to get an abortion this year, when she had a pregnancy scare. On a day when the Republican Party was forcing a gratuitous vote on abortion, could there be a more exquisite reminder that politicians’ embrace of divisive cultural wedge issues is often less than principled?

Even if Mr. Murphy’s staunchly antiabortion stance had been sincere before he had to make a decision that would affect his own life, his example underscores a truth about the abortion issue. It is far easier to judge people struggling with whether to terminate a pregnancy than it is to personally embrace the decision that antiabortion activists would demand the government force them to make. Many in the antiabortion camp would struggle when confronted with the reality of an unwanted pregnancy. Some in this situation seek the aid of friends, family or religious counselors. With more and more restrictions on legal abortion, others would seek the help of unregulated and unscrupulous illegal abortion operations or dangerous at-home remedies.

Of course, there are antiabortion advocates who live their principles with more consistency than Mr. Murphy, who announced Thursday that he was resigning from Congress . People of goodwill disagree about when life begins and mourn what they see as the morally disturbing decisions others make. But in a free society, and in the absence of a clear scientific standard, such decisions should remain with the consciences of individuals, not a matter of federal fiat. The Constitution demands as much.

Mid- and late-term abortions are already extremely rare, and a common motivation is concern that fetuses are developing with severe abnormalities. The House bill would allow no exception for this circumstance. It would represent an unforgiving assault on the freedom to choose.