Last year the Muscular Dystrophy Association announced that Jerry Lewis was stepping down as host of its annual Labor Day telethon, the marathon TV event he had made his personal showcase, soap box and sentimental journey for 45 years.

With the show cut from 21.5 hours to just 6, Jerry Lewis was being replaced by a quartet of hosts, the MDA said, and would make an appearance only at the end of the show, to say goodbye and sing You’ll Never Walk Alone one last time.

Then what seemed the sad but inevitable end of an era became something uglier. A few weeks before the show, the MDA issued a curt announcement that Jerry Lewis would not be making a goodbye appearance after all — and was resigning from his post as MDA national chairman. The telethon went on without him (raising $61.5 million in 2011, more than the previous year with Jerry Lewis, according to the MDA) and included a filmed tribute to him and warm words of thanks from various participants during the show.

A year later, Jerry Lewis has been all but erased from the telethon’s memory. This year’s show, aired the Sunday night before Labor Day, has been further downsized, to just three hours, with no named host and a smattering of B-list guest stars (Carrie Underwood, Will.i.am, Khloe Kardashian). It is no longer called a telethon, but simply an “entertainment special,” and there will be no tote board tallying the donations. In the press announcement of the event, Jerry Lewis’s name is nowhere mentioned.

The story behind Jerry Lewis’s departure remains untold. But a few things have become clear in the year since the awkward public breakup. Jerry Lewis was dumped by the MDA, the charity he had been identified with since the 1950s. He’s still bitter about it. And the telethon is withering without him.

Jerry Lewis still won’t talk about what happened.

“That’s not a place I want to go. Because if I go there, you’ll never get me back,” Jerry Lewis said when he was asked recently in Nashville, where he’s directing a new stage musical, The Nutty Professor.

“It’s not that I don’t want to talk about it. But I have already ingested all that I want from that whole f***ing adventure.”

The pain is not hard to discern. “This was a hurt man,” says Richard Belzer, the stand-up comic and Law and Order co-star, who has developed a close, almost father-son relationship with Jerry Lewis.

Jerry Lewis’ goodbye appearance was scrapped after he and the charity could not agree on its format and length. He wanted to do it live; the MDA floated several pre-taped options — “all insulting,” Richard Belzer claims.

“It’s as if they were trying to provoke him to leave.”

In the end, he did.

“It was a moral outrage, a PR nightmare and a sad commentary on this incredible philanthropic career,” says Richard Belzer.

To be sure, dealing with Jerry Lewis, now 86, has never been a walk in the park. His annual Labor Day orgy of sentiment, self-regard and showbiz schmaltz was for many years something of a punch line.

“You know why they love Jerry Lewis in France,” a comedian said not long ago.

“In France, they don’t get the telethon.”

Still, he raised an estimated $2 billion for “Jerry’s kids” over more than a half-century with the MDA, and a well-orchestrated, celebrity-studded farewell to him on the telethon might have been a fundraising bonanza.

MDA officials continue to maintain that Jerry Lewis simply retired.

“We honor Jerry Lewis, we admire the work he’s done for us, and we respect his decision to retire,” says Valerie Cwik, the MDA’s interim president.

Valerie Cwik replaced Gerald Weinberg, who was reportedly behind Jerry Lewis’ ouster and who stepped down as president last December, after 54 years with the organization.

And she insists that the changes in the telethon are part of a necessary evolution in fundraising strategy, to put less emphasis on the once-a-year event.

“It has to change because the American audience has changed,” says Valerie Cwik.

“A 21.5-hour show doesn’t fit in a 140-character world.”

Neither, apparently, does Jerry Lewis.