When was the last time America had a “legitimate” president?

You’d have to go back a ways to find a unanimous choice. Certainly not Donald Trump. Representative John Lewis, the civil-rights icon, has sparked a fury by saying, “I don't see this president-elect as a legitimate president.” Had Hillary Clinton won, she would not have fit the bill, either: Trump said repeatedly during the campaign that she should not have been allowed to run. Certainly not Barack Obama. Many opponents—none of them more prominent than Trump, yet again—argued, falsely and preposterously, that he was not even eligible to stand for the presidency because he had not been born in the United States. And certainly not George W. Bush, whom many Democrats viewed as illegitimate for several reasons: his popular-vote loss; questions over the final count in Florida; the fact that the Supreme Court effectively decided the election on a party-line vote.

Shoot, even Bill Clinton had his detractors. Well, detractor, singular. Representative Bob Dornan of California made a habit of going after the 42nd president, who he called “a small man in a big office and an illegitimate president” and on another occasion “this illegitimate president ... a serial adulterer ... a triple draft-dodger.”

The fact that you’d have to go reach back as far as 2000—or even 1992—for a  president unanimously accepted by Congress as legitimate doesn’t make the controversy over whether Trump is legitimate any less interesting. Lewis is only the most visible exponent of the argument. The Georgia representative cited what top U.S. officials, as well as Trump, have acknowledged as Russian hacking intended to influence the presidential election to hurt Hillary Clinton and aid Trump. There are now almost 60 Democratic members of the House who have publicly announced that they are skipping the inaugural festivities to register their disapproval of Trump. (Politico notes that skipping is actually not that unusual, but given the heavily mannered traditions of the the transfer of power, splashy announcements are unusual.)

There are other arguments for why Trump should be viewed as illegitimate. One is that FBI Director James Comey’s statements about the investigation into Hillary Clinton’s use of a private email server unfairly tipped the scales toward him. Another is that, like Bush, Trump lost the popular vote, though by a much larger margin.

Surely there is a hypothetical scenario in which a U.S. president might be widely and rightly considered illegitimate. Perhaps the discovery of ballot boxes full of hundreds of thousands of fake ballots, which if subtracted from the vote total would have swung the outcome. Yet most of the actual arguments about illegitimate presidents have trouble standing up to scrutiny. Did Russian hacking or Comey’s statements influence some voters’ decisions? Certainly. But isolating the specific effects of either is impossible. Meanwhile, there are other factors that also affected the final tally. Given the close margins in  several states, it’s conceivable that a better tactical approach by Clinton’s campaign might have produced a victory anyway.

Even so, the po-faced condemnations from some Republicans are rather hard to take seriously, given the fervor with which Trump and some other elected officials espoused the “birther” lie that Obama was not born in Hawaii, which was entirely baseless. Demands that Obama now speak forcefully against the crowd calling Trump illegitimate would be more credible had not so many Republicans—including quite a few, such as Mitt Romney, who did not espouse the birther lie themselves—been mostly willing to look the other way when conservative and GOP figures were insisting Obama was illegitimate. (Obama has, according to Trump aides, been helpful to Trump during the transition period, and during his farewell address last week offered a rousing defense of the transition to the new president.)

What happens after these declarations of illegitimacy? In the immediate term, they appear to make very little difference. Mostly, people come around and move on. Obama won reelection handily in 2012, and he leaves office with fairly strong approval ratings. George W. Bush won reelection in 2004, and while a few fringe figures argued the election was hacked, most accepted it. When Bush left office in 2009, he was intensely unpopular, but as a result of the policies he pursued, not because he was viewed as an imposter. As Carl Cannon and Caitlin Huey-Burns write in RealClearPolitics today, there’s an interesting footnote to the Bush story. John Lewis skipped that inauguration, too. When he announced his boycott this year, he claimed it was the first he’d missed since entering Congress, and then had to acknowledge he was wrong. Yet Lewis now says that he calls Bush “a friend.

So, is all well that ends with legitimacy? It’s hard to imagine that having three consecutive presidents who have been labeled illegitimate by visible portions of the opposition party doesn’t have a corrosive effect on democracy. Over time, the accusations seem to have migrated from the fringe—Dornan was a notorious crank, and the newly elected Republican Congress censured him in 1995 for his broadsides against Clinton—to the center, as represented by the chief birther’s ascension to the White House.

Trump’s election might represent the logical end of constant insistence that successive presidents are illegitimate. Trump was a historically dishonest candidate. Exit polls found that voters viewed him unfavorably by a wide margin, wider even than they did Clinton, and believed that neither his resume nor his temperament qualified him for office. And yet many of the same voters who held that view voted for Trump anyway. They were disgusted with America’s institutions, and told reporters time and again that while they had hesitations about the candidate, they wanted someone who would shake up the whole rotten system—which they believed Trump could do.

When the leaders of America’s political institutions are willing to label their opponents as illegitimate, they may end up convincing voters that the institutions themselves are corrupt—and that any change at all has to be for the better.