It’s an unspoken rule in the presidential playbook: Be firm, show emotion, but don’t cry.

Just last month, Newt Gingrich exhibited it with his denunciation of the media in a debate that became the key to his unexpected South Carolina triumph.

Four years ago, Hillary Clinton also showed how it was done. She turned her fortunes around the day before the New Hampshire primary she seemed certain to lose. Ever so close to the brink of crying but short of actual tears, she came forth with her famous, “I just don’t want to see us fall backwards,” lament.

Often, when in a race for the White House, such emotions evoke a reference to Maine’s Edmund Muskie. As Maureen Dowd observed about Clinton in 2008: “Here was Hillary doing the Muskie.”

Now, on the 40th anniversary of one of the most pronounced moments in presidential politics, it’s a fitting occasion to take a close look at it.

It was February 1972. Since July of 1969, then-Sen. Muskie was the prohibitive frontrunner for the Democratic presidential nomination. As CBS’s Eric Severeid, then the dean of network news commentators, said, “Unless this man steps on a land mine he will be nominated.”

Gallup polls had shown Muskie as the only Democrat who matched evenly with Republican President Richard Nixon, then seeking re-election.

Crucial to sustaining Muskie’s momentum was the early March primary in New Hampshire, where the Maine senator had near favorite-son status. He was expected to win with a two to one margin over all his opponents combined.

Less than two weeks before the primary, the state’s largest newspaper, William Loeb’s Manchester Union Leader published two pieces that seized the attention of the Muskie campaign.

The first was a front-page editorial headlined, “Senator Muskie Insults Franco-Americans.” Loeb accused Muskie of condoning the use of “Canuck,” a term sometimes asserted to be a derogatory designation for French Canadians, comprising 40 percent of New Hampshire Democrats.

The editorial was based on a letter purportedly sent to the Union Leader by a Paul Morrison. In it, “Morrison” wrote that a Muskie aide in Florida had said, “We don’t have blacks [in Maine], but we have Cannocks” (sic).

To this, Muskie was quoted as laughingly replying, “Come to New England and see.”

(Authorship of the letter was never determined conclusively, though it was later by some attributed to Ken Clawson, a White House communications director.)

The next day, Loeb reprinted a brief, 2-month-old Newsweek item about Muskie’s wife, Jane. It contained innuendo that Mrs. Muskie had a proclivity for telling dirty jokes, for drinking pre-dinner cocktails and for smoking cigarettes in secret.

The mutual animosity between Muskie and Loeb dated to 1957, after Loeb successfully kept a Peyton Place movie film crew from shooting in New Hampshire. Muskie, then Maine’s governor, allowed the somewhat carnally suggestive picture to be filmed in Camden, earning him a fierce denouncement from Loeb.

The “Canuck” and Jane Muskie writeups were the final straw for Muskie. In a campaign where Muskie was sometimes portrayed as lacking “fire” or passion, most of his staff — including deputy manager George Mitchell — advised the senator to take on Loeb to show, in Mitchell’s words “a fighting Ed Muskie.”

The next day, Muskie mounted a flat-bed truck in front of the newspaper’s office. He started by refuting the Canuck letter, reserving his greatest ire for the attack on Jane.

Muskie, after calling Loeb a “gutless coward,” passionately praised his wife as a “good woman.” He then paused for nearly half a minute, heaving his shoulders, rubbing his nose, obviously shaken and unable to speak.

The large, wet heavy snow flakes dropping — and melting — on his face seemed, to some observers, to be commingled with tears. Syndicated columnist David Broder and Time magazine were among those that so reported the event. “Crying out loud” was the caption below a Time photo of Muskie, for example.

Without tears, the Muskie presentation — like the “Hillary moment” of 2008 — might well have galvanized support and sympathy for the presidential candidate. But with the perception — even if not justified — that tears had in fact flowed, Muskie appeared personally weak, and unnecessarily troubled and vulnerable.

(Not all of Muskie’s leading supporters had thought that confronting Loeb was a good idea. Severin Beliveau recalled recently that he tried to talk Muskie out of it. Beliveau noted, for example, that Franco-Americans such as himself were not offended by the “Canuck” expression, which had long been associated with the Vancouver hockey team, for example.)

In the March 7th voting, Muskie was the nominal victor. But his tepid 47-percent showing — just nine points ahead of second-place finisher George McGovern — was well below expectations. Muskie’s campaign never recovered, and within a few weeks he dropped out of the race.

The sustaining lesson from Muskie’s indelible moment and its enduring epitaph? There is no crying in presidential politics.

Paul H. Mills is a Farmington attorney known for his analyses and historical understanding of Maine’s political scene. Email at [email protected]