Direct mail gets less attention than television commercials or campaign events. Yet it is a battleground in the presidential race, as the campaigns and their proxies communicate privately with voters.

Take a recent mailing from the American Civil Liberties Union. “I’m writing you today with an urgent plea for your participation,” says the letter, signed by the executive director of the ACLU, Anthony Romero. Then, in boldfaced type: “Fueled by racial animosity and political desperation, Trump won’t stop at anything to keep people from the polls this November.”

Mailing letters to voters just weeks before early or mail-in voting starts, describing one of the two presidential candidates, by name, as motivated by “racial animosity” and as attempting to prevent in-person voting — when in fact President Trump has encouraged people to go to the polls — is the sort of thing you’d ordinarily see from a political party or an actual candidate’s campaign, not a nonprofit organization such as the ACLU. The tax return the ACLU filed in November 2019 cites the organization’s articles of incorporation in stating, “The ACLU’s objects should be sought wholly without political partisanship.”

“Should,” yes. Whether they are is, nowadays, another matter entirely. The same tax return lists an ACLU staffer with the title “national political director,” with annual compensation of $346,012. That staffer, Faiz Shakir, left the ACLU to serve as campaign manager to the Bernie Sanders presidential campaign.

In June 2018, the New Yorker reported, “The A.C.L.U. Is Getting Involved in Elections — And Reinventing Itself for the Trump Era.” The group had previously been “fastidiously nonpartisan,” the New Yorker said, quoting the organization’s former executive director, Ira Glasser, describing the “transformative change” as “a departure which has the capacity to destroy the organization.”

I asked the ACLU how the direct mail piece with the line about Mr. Trump is consistent with the “without political partisanship” claim in the tax return. I also asked whether it erodes the credibility of the ACLU on civil liberties issues to be seen as just another partisan political campaign organization. The ACLU did not respond to my inquiry.

The ACLU is a big operation, reporting about $146 million in expenses on that tax return filed in November 2019. The ACLU Foundation, an affiliated nonprofit, listed revenue of about $205 million and assets of about $371 million on its tax return filed in November 2019.

It’s ironical, because the ACLU website carries an article headlined “Buying Elections Is Not Free Speech,” accusing “big corporations” of “crying ‘free speech’ and fighting tooth-and-nail to hide the funding of their electioneering efforts from the voting public.”

In general, the ACLU has been less enthusiastic about campaign speech regulation than the rest of the organized left or even than the late Republican Senator John McCain. The presidential candidate that the ACLU is trying to help get elected, Vice President Biden, voted with Senators McCain and Feingold for the Bipartisan Campaign Reform Act of 2002.

That law, parts of which were later struck down by the Supreme Court as unconstitutional violations of the First Amendment guarantees of free speech, would have sharply restricted the ACLU’s ability to send mail of the sort it is sending about Mr. Trump without registering as a political committee and subjecting itself to all sorts of onerous disclosure requirements and other limits.

Mr. Biden is also no friend of the Second Amendment right to bear arms. That is something voters concerned with civil liberties might consider, though it is not mentioned at all in the ACLU’s pre-election mailing.

How many of those letters were sent? To voters in what states or congressional districts? At what expense? Who paid? Were the funders of the mailing all U.S. citizens? If not, what other countries were they citizens of?

I’m not terribly worried about any of these things, figuring that voters will be smart enough to sort it out for themselves. The left, though, has been insisting, on not much evidence, that Russian Facebook ads determined the outcome of the 2016 election. If one wants to take the position that American voters are so easily manipulated that every last cent spent on the election should be publicly tracked and disclosed, it’s hard to see the consistency in applying that position only to pro-Trump spending but not to anti-Trump spending.

The writer and editor Bari Weiss recently tweeted, “If you are looking for an example of institutional capture — the abandonment of mission, the hollowing out of an essential American organization from within — I’m not sure you can do better than the ACLU.” Do not expect much curiosity about that public policy issue from a President Biden that the ACLU could claim credit for helping to elect.