Democrats Keep Hoping It’s Curtains for Trump. He’s Still Center Stage.

For as long as Donald J. Trump has dominated Republican politics, many Democrats have pined for a magical cure-all to rid them of his presence.

There was the Mueller investigation into Mr. Trump’s 2016 campaign and its ties to Russia, which began four months into his presidency. Then came the first impeachment. Then, after Mr. Trump lost the 2020 election and his supporters stormed the Capitol, the second impeachment.

Each time, Democrats entertained visions of Mr. Trump meeting his political downfall. Each time, they were disappointed.

This year, liberal hopes have sprung anew, with federal and state prosecutors bringing 91 felony charges against Mr. Trump in four criminal cases.

Then, on Tuesday, came what appeared to be an out-of-the-blue act of deliverance from Denver. Colorado’s top court ruled that Mr. Trump should be disqualified from holding office on the grounds that he incited an insurrection on Jan. 6, 2021, a decision that is likely to end up at the U.S. Supreme Court.

Once again, Democrats find themselves looking toward American institutions to stop Mr. Trump, whom they view as a mortal threat to democracy. For many, it may be more pleasant to think about a judicial endgame that stops Mr. Trump than envisioning the slog of next year’s likely rematch against President Biden.

And this time, with Democrats now well aware of how easily he can bend the country’s fragile guardrails — and of the Supreme Court’s conservative majority, which includes three Trump appointees — their optimism is tinged with trepidation.

“Like many people, I assumed every impeachment, every indictment, every criminal count would be the end of him,” said Robert B. Reich, a former labor secretary who for a time hosted a podcast called “The Resistance Report.”

Mr. Reich said he did not believe the Supreme Court would block the former president from the ballot. But by the end of an interview on Wednesday, he had almost talked himself into the possibility that it might happen.

“If the Supreme Court affirmed the Colorado Supreme Court, then we’re in a different legal land and a lot different political land,” Mr. Reich said. “That could have implications for every state.”

Throughout Mr. Trump’s career in office, Republican voters and many of the party’s elected officials have protected him from punishment.

The one time when his future in politics appeared in serious doubt, the Senate fell 10 votes short of convicting him of inciting an insurrection, with most Republicans in the chamber finding reasons to stick by him and not disqualify him from holding future federal office.

“There has been a sense of a lot of moments of potential accountability for Donald Trump,” said Noah Bookbinder, the president of Citizens for Responsibility and Ethics in Washington, the watchdog group that brought the Colorado case. “What we’ve seen time and time again is decision makers passing on opportunities to provide meaningful accountability because they assumed that somebody else would do it.”

When that moment of accountability in early 2021 passed, it left open the prospect of another Trump presidential campaign, which has now become the gravest threat to Mr. Biden’s re-election.

With this in mind, some Resistance-era Democrats are sizing up the Colorado decision, and whether it could actually prompt the Supreme Court to block Mr. Trump from ballots nationwide.

“I think many of us learned with Mueller that it’s a lot easier to have zero expectations and be pleasantly surprised if something goes the way you want,” said Adam Parkhomenko, a Democratic strategist who founded the Ready for Hillary super PAC before becoming a familiar figure in the social media opposition to Mr. Trump. “There’s just so many balls in the air now. You kind of wonder what will be the first to drop that could actually be the endgame for him.”

Even Mr. Biden, who has steered clear of commenting on Mr. Trump’s criminal charges, couldn’t help weighing in on the prospect that his rival might be knocked off the ballot.

Speaking to reporters after disembarking Air Force One in Milwaukee on Wednesday, Mr. Biden initially said he would not comment on the Colorado ruling. The White House had said nothing, and a spokesman for his 2024 operation said on Tuesday night that the campaign would not, either.

Then Mr. Biden opened up.

“It’s self-evident. You saw it all,” he said. “He certainly supported an insurrection. No question about it. None. Zero.”

Other Democrats shared his view, and went even further.

Jon Cooper, a former Long Island county legislator who regularly predicted on social media that one scandal or another would force Mr. Trump’s resignation, professed confidence that the Colorado case would finally stop Mr. Trump.

Mr. Cooper, who still posts frequently to his 1.3 million followers on X, said he was not overly worried that this moment would again resemble Lucy Van Pelt pulling back the football just before Charlie Brown can kick it.

“Count me among those who think that there’s a good chance that the U.S. Supreme Court will uphold the Colorado Supreme Court ruling,” Mr. Cooper said on Wednesday. “I am an optimist.”