I wrote here about the British Left’s disgraceful effort to make political hay out of the murder of Labour MP Jo Cox by a mentally ill man. Pro-EU forces are trying to somehow tie the murder to the “Brexit” side of the EU debate. While I considered the attempt contemptible, I wasn’t at all sure that it wouldn’t work. (The parallels to similar issues in the U.S. are obvious.)

But if this survey is right, the Left’s effort may be failing:

British support for remaining in the European Union has weakened in the wake of the murder of the pro-EU politician Jo Cox, according to an online research company Friday. Qriously, a London-based technology start-up that gathers data and intelligence about consumers through mobile phone apps, found that backing among likely voters for Britain’s EU membership has dropped to 32% from 40% before her death. The poll was based on 1,992 British adults surveyed on June 13-16, and then 1,002 on June 17 — the day after Cox was shot and killed in northern England. … Qriously found that 52% will vote to leave the bloc in a national referendum on June 23. The figure is unchanged from before the parliamentarian’s death. The weakening support for remaining in the EU coincided with a large move toward “Don’t know,” which leaped to 16% from 9% before Cox’s assassination.

In recent weeks, momentum has shifted toward the Brexit side. If this poll is reliable, it suggests that such movement continues, and the tragic murder of Ms. Cox has not changed how Britons think about remaining in the EU. Nor, of course, should it.