When Hillary Clinton gave her concession speech acknowledging that she’d lost to Donald Trump in the presidential election, she broke with tradition in several ways.

First, she wore purple, departing from the typical red, white, and blue worn by male presidential hopefuls. But her speech also contained a word that no other presidential candidate has said when conceding the election: “sorry.”

Fortune analyzed the transcripts of past concession speeches in U.S. presidential elections going back to 1952, when Democratic nominee Adlai Stevenson, defeated by Dwight D. Eisenhower, delivered the first televised concession speech—one that has been considered a model for other election losers in modern history. In all of those male candidates’ addresses, not one of them ever apologized.

But Clinton was different.

“I’m sorry that we did not win this election for the values we share and the vision we hold for our country,” Clinton said Wednesday (see the full transcript of her concession speech). “I know how disappointed you feel, because I feel it too,” she added.

Clinton’s apology was perhaps an appropriate message to supporters who reacted to her shocking loss with grief—so much so that Saturday Night Live’s opening skit this weekend featured its Clinton character, played by Kate McKinnon, singing a mournful rendition of “Hallelujah”, as though at a funeral.

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But the phrase “I’m sorry” has also come to be loaded with issues of gender bias and sexism. As Fortune has previously pointed out, women are especially prone to apologizing, even when they have done nothing wrong. It’s gotten to the point that some female executives have adopted a so-called “Sorry Jar,” charging their women colleagues a $1 penalty every time they say the word in order to encourage them to break the habit.

Researchers have suggested that men are simply more reluctant to admit wrongdoing than women, particularly for minor offenses. Others argue that women—especially those in positions of power, whether in the workplace or elsewhere—fall back on saying “I’m sorry” as a way of making themselves seem softer or less threatening, as aggressive characteristics have been shown to stunt women’s careers much more so than men’s.

Throughout Clinton’s campaign, critics urged the female candidate to alter her demeanor—such as by asking her to smile more or to change her tone of voice—apparent attempts to blunt her characteristics that came across as too aggressive or unfeminine. Such critiques are more frequently lobbed at women than they are at men, Fortune’s Valentina Zarya points out.

Trump, meanwhile, has notoriously resisted apologizing to those he has insulted, despite repeated demands that he do so. The only time Trump publicly apologized during his campaign was in October, after he was confronted with a recording of his crude remarks about groping women: “I was wrong, and I apologize,” Trump said—stopping short of actually saying the word “sorry.”

In terms of election outcomes that were a particularly painful letdown for at least half the country, the 2000 race between Republican George W. Bush and Democrat Al Gore rivaled the Clinton-Trump contest in 2016. After initial vote tallies were too close to call, sending the decision to the U.S. Supreme Court, Gore had to finally concede to Bush more than a month later.

Still, Gore did not apologize in his concession speech ending the bitter campaign. “I know that many of my supporters are disappointed. I am too. But our disappointment must be overcome by our love of country….Some have asked whether I have any regrets. And I do have one regret—that I didn’t get the chance to stay and fight for the American people over the next four years, especially for those who need burdens lifted and barriers removed, especially for those who feel their voices have not been heard,” Gore said in his speech.