MSNBC announced on Monday that, “per network policy,” presidential historian Jon Meacham would no longer be serving as a MSNBC contributor. “He will be welcome as a guest with full disclosure of his involvement with President-elect Joe Biden’s team,” noted a network spokesperson.

Who will be MSNBC’s expert on “norms” from now on? The Pulitzer Prize-winning author of books on America’s soul, Andrew Jackson, George H.W. Bush and, recently, John Lewis (among other titles), Meacham had been a regular on MSNBC’s reliably anti-Trump programming, a voice of historical authority who could contextualize just how far Trump had veered from governing standards in the United States — a full detour, as Meacham explained over and over.

He’ll now have to join those panels as an unpaid guest of the network. Impetus for the network’s abrupt announcement came from New York Times reporters Annie Karni and John Koblin, who reported that Meacham had been working with the Biden team on speeches, including the president-elect’s Saturday night address.

In a swampy moment, Meacham appeared on MSNBC following the speech. Asked if Biden’s presentation aligned with U.S. presidential traditions, Meacham responded, “Absolutely.” Showing perhaps a greater command of U.S. history than of journalism ethics, Meacham didn’t disclose that the wonderful speech came, at least in part, from his own thoughts. Instead, he plowed ahead with his analysis. “Tonight marks — the entire election results mark — a renewal of an American conversation where we’re struggling imperfectly to realize the full implications of the Jeffersonian promise of equality,” said Meacham. “It’s taken us too long, our work has been bloody and tragic and painful and difficult and, Lord knows, it is unfinished, but at our best we try.”

Meacham also credited Biden for a moment in his speech when he cited all the firsts in Kamala Harris’s ascent — first woman, African American woman and South Asian woman to be elected vice president. “It’s long overdue, and we’re reminded tonight of all those who fought so hard for so many years to make this happen. But once again, America has bent the arc of the moral universe toward justice,” said Biden.

Now: The moral-arc-justice line has become something of a speechy cliche. It was a favorite of President Obama, who had it sewn into the rug in the Oval Office. The exact wording of the quote comes from Martin Luther King Jr., who was paraphrasing the thoughts of 19th century abolitionist Theodore Parker. It’s no surprise that Meacham cited Biden’s invocation of that theme: He used it in his own speech back on Aug. 20, when he endorsed the Biden-Harris team during the virtual Democratic National Convention. “Bending that arc requires all of us, it requires we the people and it requires a president of the United States with empathy, grace, a big heart and an open mind. Joe Biden will be such a president,” said Meacham, who has a bipartisan presidential voting history.

In introducing himself to the virtual convention audience, Meacham said that he was a historian. There was no mention of his affiliation with MSNBC. The address was broadcast on MSNBC’s very own air, where, you might suppose, it would have raised a red flag. After all, just a couple of weeks earlier, MSNBC told The Post’s Jeremy Barr that the “network’s contributors cannot endorse candidates — or get into a race.” But a source close to Meacham says MSNBC was informed of and approved Meacham’s DNC appearance. The network did not return a request for comment.

Indeed, it appeared that the network was proud of the moment. Days after the speech, Meacham appeared on the afternoon show “Deadline: White House.” Host Nicolle Wallace played a clip from the historian’s speech and said, “That was Jon Meacham during last week’s Democratic National Convention making the case for Joe Biden. It was a rare appearance from a presidential historian, supporting a candidate for a president. But, of course, these are not normal times, not even close, and Donald Trump constantly reminds us of that as he obliterates the lines between campaigning for a second term and governing.”

Crosscutting allegiances and dalliances have long skewed on-air commentary. Forty years ago, George Will assisted Republican presidential candidate Ronald Reagan to prepare for a debate with Jimmy Carter. Afterward, Will appeared on ABC News with favorable commentary on Reagan’s showing. In what was supposed to have been a defense, then-ABC News President Roone Arledge said viewers weren’t hoodwinked because Will was a ''known partisan.'' In a 2005 column in The Post, Will termed his assistance “as inappropriate as it was superfluous — after three decades of public advocacy, Reagan was ready."

On a more contemporary front, the Intercept showed how pro-Hillary Clinton pundits in the 2016 presidential cycle carried significant conflicts onto the airwaves. Newt Gingrich, working in 2013 as a polemical combatant on the reboot of “Crossfire,” was involved in a PAC that donated to a Republican senator who had been a guest on the show.

CNN issued a risible dodge in explaining away Gingrich’s ethical lapses: “We are clarifying the policy and making it clear Newt Gingrich is not in violation. The policy: If a Crossfire co-host has made a financial contribution to a politician who appears on the program or is the focus of the program, disclosure is not required during the show since the co-host’s political support is obvious by his or her point of view expressed on the program.”

That contrived “policy” is a sham, and so are others like it. Of course it’s not surprising that a guy like Gingrich would support Republican politicians and criticize Democrats. Entanglements such as donations and speechwriting, however, take relationships to a deeper footing, one that submerges independence and candor. Coziness begets predictability and boredom.

Yet it’s everywhere on cable news. Over at CNN, contributor Jen Psaki, a prominent communications aide in the Obama administration, just vacated the payroll after she signed up as an adviser with the Biden-Harris transition team. She promptly gave an interview to Anderson Cooper in that latter capacity. How are viewers to keep up with shifting titles?

The pundits the networks most prize, it seems, are precisely the ones who remain in the game — orchestrating PACs, dishing out endorsements, consulting with key players, tweeting. There’s no better demonstration of this dynamic than the past several days, as NBC News/MSNBC has had to part ways with four network contributors — Meacham, Dr. Ezekiel Emanuel, Barbara McQuade and Richard Stengel — because of various ties with the Biden operation.

Hey MSNBC: You’re supposed to be challenging Fox News in viewer ratings, not in the number of folks that you feed into the White House! It still has quite a ways to go, in fairness, to rival the corruption of the Fox News-White House relationship.

One alternative to all the contributor madness would be to turn over the airwaves to people hired to report facts and scoops and required to avoid affiliations with outside organizations. Those folks are known as journalists.