Yvette Clarke, a Democratic congresswoman from Brooklyn, New York, had initially planned on attending Donald Trump’s inauguration out of respect for tradition and the institution of the presidency. But last week, she started to waver. “We had the opportunity as members of Congress to attend the intelligence community briefing about what took place in terms of hacking and the intrusion of the Russian government into our electoral processes,” she told me. “I’d always been concerned about it, but until the briefing, I didn’t realize the breadth and depth of what took place.” Then, on Friday, Trump took to Twitter to insult civil rights hero Rep. John Lewis, who had said he doesn’t see Trump as a legitimate president. “All talk, talk, talk - no action or results,” Trump tweeted about Lewis, a former Freedom Rider who was beaten nearly to death marching from Selma to Montgomery, Alabama. It was, says Clarke, the “nail in the coffin.” Lewis had said he wasn’t going to the inauguration, and Clarke announced that she was staying away as well. “I believe in the peaceful transfer of power,” Clarke says. “I also believe in the peaceful right to protest.”

Soon the boycott snowballed. As of this writing, nearly 70 members of Congress—more than one-third of the Democratic caucus—are skipping Trump’s inauguration. So is Secretary of State John Kerry. Lewis’ words, and Trump’s reaction to them, set off a cascade as one Democrat after another realized that there was no reason to pay Trump the respect typically given American presidents. “You’re actually seeing a huge reaction to the cloud of illegitimacy over Donald Trump,” California Rep. Ted Lieu, who is also boycotting the inauguration, tells me. Says Texas Rep. Lloyd Doggett: “I think it’s an important message we are sending to Mr. Trump, that you will get no cooperation if you provide no cooperation. You will get no respect if you provide no respect.”

The last time members of Congress staged a protest like this was in 1973, when 80 anti-war representatives refused to attend Richard Nixon’s second inauguration. True, a few Democrats, including Lewis and California Rep. Barbara Lee, skipped George W. Bush’s inauguration in 2001. But even though Bush lost the popular vote and assumed the presidency thanks to a Supreme Court ruling, most Democrats refrained from questioning his legitimacy and instead worked to shore up popular faith in our democracy. The attitude then, says Doggett, was, “Let’s honor this peaceful transition in our democracy. That’s important even though it came about in a very unjust way.”

But Democrats feel that their good faith wasn’t repaid and are increasingly unwilling to remain bound by political manners that their opponents refuse to heed. They have finally realized that, faced with an opposition with a limitless will to power, they cannot preserve collegial bipartisan processes alone. “Now we have that experience behind us,” Doggett says of the Bush years. “We have to look at what a terrible price we have paid for having George W. Bush instead of Al Gore as president. Now, as we consider an even more outrageous Republican president, given that experience, I think it’s essential that we use every nonviolent way that we can of resisting Trumpism.”

Not every Democrat who is skipping the inauguration describes Trump as illegitimate. Some simply say they can’t pretend to celebrate an event that they and their constituents regard as a calamity. “I made a decision shortly after the election that I didn’t think, in good conscience, I should dignify what should be a solemn and very significant occasion with my presence,” says Oregon Rep. Earl Blumenauer. “Mr. Trump ran what I think is arguably the most disgraceful election in our nation’s history.”

Yet Democrats are increasingly willing to say that Trump’s election was not just tragic but tainted, and that he may not have any right to the office he’s about to assume. Like Clarke, Lieu says he was shaken by what he learned in the classified intelligence briefing about Russian hacking. “The classified report provides clear and convincing information to support the conclusions set forward in the unclassified report,” he says. He’s been infuriated by Trump’s attempt to raise doubts about the intelligence community’s findings. “He is lying to the American people when he said that some other country may have hacked us,” says Lieu. “It was Russia. Trump went to the briefing. He knows what’s in that report, and he is lying to the American people.”

Lieu sees other reasons to question Trump’s legitimacy. “He will be in violation of the constitution the second he is done swearing in his oath of office,” Lieu says. “He has massive foreign conflicts of interest. He can fix that by divesting his global business holdings or putting them in a blind trust. He refuses to do so. He also refuses to release his tax returns as he said he would. That would let the American people know if he has any special interests in Russia.”

Not surprisingly, conservatives are accusing Democrats of hypocrisy, since Democrats denounced Trump for his campaign to delegitimize Barack Obama and worried that he’d refuse to accept an election loss. “Back in October, when Trump foolishly suggested he might not accept the results of the election, it was considered a threat to democracy,” John Daniel Davidson writes at the Federalist. “Now, it’s an act of patriotism.” Davidson decries a “sinister trend, common to both sides, of routinely attempting to delegitimize the opposition.”

This argument has a surface logic, but it depends on ignoring the underlying facts. Trump threatened to call the election results into question based on fantasies about voter fraud. Democrats are questioning the results based upon the findings of America’s 17 intelligence agencies. Trump attacked Obama’s claim to the presidency with racist lies about his nationality. Democrats are attacking Trump’s by demanding the truth about his financial holdings. “If our 17 intelligence agencies had a high confidence that Barack Obama faked his birth certificate, absolutely there would have been a huge legitimacy crisis,” Lieu says wryly.

Anyway, many Democrats, particularly those in deep-blue districts, are past worrying about what Republicans think of them. “They’re being disingenuous,” says Barbara Lee. “Let them say what they want to say. They can keep criticizing us. We’ve got to be real with people. We’ve got to be the voice of the people.” Tennessee Rep. Steve Cohen has come to the conclusion that the right will smear Democrats no matter what they do, so they might as well do what they think is right. “There are two different worlds,” he says. “One world is tolerant and accepting and diverse and, in my opinion, thoughtful. It’s two different worlds, and it’s hard to see where there’s a bridge.”

In such a polarized climate, Democrats are less worried than they once were about appealing to an elusive center or winning the approval of bipartisan eminences in Washington. “It used to be that Democrats were terrified about what the centrist establishment would say about them if they showed spine or, heaven forfend, bared their teeth,” says Ben Wikler, Washington director of MoveOn.org, which is calling for all Democratic lawmakers to boycott the inauguration. “But now that establishment has been eviscerated. It has been shown to have no power whatsoever. Democrats can see that fighting back is the only option. And they can already tell that they’re going to catch hell from their grass-roots activists if they don’t do it.”

It’s not clear that the defiant posture will last. Doggett predicts that during the inauguration, Trump will offer a few conciliatory remarks about bringing the country together. “I’m confident that there will be some fawning comments about how he’s finally beginning to act presidential, and let’s come together for the good of the country,” Doggett says. The pressure on Democrats to collaborate with Trump could become intense. “I’m hopeful, but we’re very early in the process, and there’s no doubt that there’s a big corporocrat section of our caucus,” he says.

But for now, a growing group of Democrats are listening to their outraged progressive constituents, most of whom want their representatives to stand up to Trump however they can. Cohen says one of his donors—a Republican—wrote to him urging him to change his mind about the inauguration, arguing, “You need to watch the peaceful transfer of power. That’s part of democracy.” Cohen doesn’t disagree; the decision to skip the inauguration was one he wrestled with. But ultimately, he says, “It’s also part of democracy to let people know that you represent their voices.”