Former President Donald J. Trump has refused to accept his loss in the 2020 election, painted as martyrs the supporters who stormed the Capitol on Jan. 6, 2021, laid groundwork to deny the 2024 election results if he loses, and said he would be a dictator on his first day back in office if he wins.

But according to the independent presidential candidate Robert F. Kennedy Jr., it is President Biden who poses the greater threat to American democracy — a view that Mr. Kennedy shares with Mr. Trump himself, and that democracy experts called “absurd” and “preposterous.”

Such a perspective is possible because Mr. Kennedy, who has founded his political career on promoting vaccine misinformation and conspiracy theories about the government, sees the Biden administration’s efforts to curtail the spread of misinformation as a seminal issue of our time. Censorship, as he calls it, overpowers all other concerns about the political system.

Mr. Kennedy’s stance drew fresh scrutiny this week after he said in an interview on CNN, “President Biden is a much worse threat to democracy, and the reason for that is President Biden is the first candidate in history, the first president in history that has used the federal agencies to censor political speech, to censor his opponent.” He repeated himself on Fox News on Tuesday, saying that a president like Mr. Biden was “a genuine threat to our democracy.”

The remarks by Mr. Kennedy, who carries the name but not the support of a storied Democratic family, were an escalation of his attacks on Mr. Biden and the Democratic Party.

He has long said that the government’s engagement with media companies and tech platforms — to prevent the spread of disinformation or illegal materials or, in Mr. Kennedy’s case, the arguments he and his allies made against vaccines — amounts to illegal censorship, an argument that was met with skepticism at the Supreme Court last month.

In the CNN and Fox News interviews, Mr. Kennedy — an environmental lawyer who until last fall was himself a Democrat — trained his outrage directly on the Democratic Party’s leader, whose allies worry that Mr. Kennedy could tip a close election in November to Mr. Trump.

Democratic officials have devoted increasing resources to a multipronged effort to undermine Mr. Kennedy’s campaign, fearing that his presence on swing-state ballots could siphon votes from Mr. Biden.

At the same time, it remains unclear whether Mr. Kennedy — whose anti-establishment message has also made him popular with some disaffected Republicans, independents and Libertarians — would draw more votes from Mr. Biden than from Mr. Trump. A recent Fox News poll showed him drawing about equally from both candidates, and Mr. Trump attacked Mr. Kennedy last week as a “radical Left” candidate, in a potential sign of nervousness about his candidacy.

In campaign appearances, Mr. Kennedy has often drawn comparisons between Mr. Biden and Mr. Trump. Last week, when he announced his running mate, Nicole Shanahan, a Silicon Valley lawyer, Mr. Kennedy said that to young Americans, Mr. Biden and Mr. Trump “look like two sides of the same coin.”

But several scholars who have studied democratic governments and the ways they can backslide told The New York Times that it was nonsensical to suggest that social media moderation — which the Supreme Court seemed inclined to uphold as a legitimate goal of government — posed a greater threat than what Mr. Trump has done.

They pointed to his refusal to accept an election loss, his stoking of political violence, and his efforts to consolidate executive power and undermine public confidence in independent sources of information.

The two most fundamental tenets of democracy are that politicians “must always unambiguously accept the results of elections and must always unambiguously reject political violence,” said Steven Levitsky, a professor of government at Harvard who co-wrote the book “How Democracies Die.” “I don’t think you’ll find a democracy expert in the world who will claim that the mild efforts to regulate social media in the United States are somehow equivalent or worse than an effort to overturn an election or the encouragement of political violence.”

Sheri Berman, a professor of political science at Barnard College, said Mr. Kennedy had not only downplayed Mr. Trump’s election denial — a threat that is “fundamental” and “has to be recognized as such if democracy is going to work,” she said — but also inflated Mr. Biden’s actions.

“If we had a president who was using federal agencies to chase down his opponents, to disadvantage them politically, to stop them from being able to speak to citizens and voters, that would be a major infringement of democratic norms,” Dr. Berman said. “That’s not what Biden was doing.”

In the CNN interview, Mr. Kennedy said Mr. Trump’s attempt to overturn the 2020 election “clearly” was a threat, but added: “The greatest threat to democracy is not somebody who questions election returns, but a president of the United States who uses the power of his office to force a social media company — Facebook, Instagram, Twitter — to open a portal and give access to that portal to the F.B.I., the C.I.A., the I.R.S., the CISA, the N.I.H., to censor his political critics.”

He then said he was not making the argument he had just made, but was simply saying it was an argument he could make.

He also did not provide evidence of any “portal” through which federal agencies can remove posts. Rather, he referred to a lawsuit he filed last year alleging that, by threatening regulatory action, the Biden administration had “induced” social media companies to restrict speech — including anti-vaccine misinformation — in ways the First Amendment would prohibit the government from doing directly.

A federal judge in February granted a preliminary injunction but stayed it until the Supreme Court rules in a related case, Murthy v. Missouri, with which Mr. Kennedy’s case was consolidated. In the meantime, the Supreme Court allowed the government, including the F.B.I., to continue contact with major social media companies — and in hearing the case last month, the justices appeared skeptical of the arguments against the government.

A lawyer for the government, Brian H. Fletcher, told the court that banning the regulation in question would itself prohibit speech, including public comments from a press secretary or other officials seeking to discourage posts that are harmful to children, antisemitic or Islamophobic. He added that the social media companies had acted independently of the government and often rejected requests to take down postings.

A senior adviser for the Democratic National Committee called Mr. Kennedy’s comments “MAGA talking points” that put to rest “any doubts that he’s a spoiler candidate.”

“With a straight face, Robert F. Kennedy Jr. said that Joe Biden is a bigger threat to democracy than Donald Trump because he was barred from pushing conspiracy theories online,” the adviser, Mary Beth Cahill, said. “There is no comparison to summoning a mob to the Capitol and promising to be a dictator on Day 1.”

In the CNN interview, Mr. Kennedy also said falsely that Mr. Biden was “the first president in history to use his power over the Secret Service to deny Secret Service protection to one of his political opponents for political reasons,” referring to the government’s refusal so far to extend protection to Mr. Kennedy.

“Major” presidential candidates are eligible for Secret Service protection but are not guaranteed it. Whether to grant protection is up to the secretary of homeland security, in consultation with congressional leaders from both major parties, and independent and third-party candidates are less likely than Democrats and Republicans to receive it.

In a fund-raising email on Tuesday morning, Mr. Kennedy’s campaign reiterated its complaints about the Biden administration and the Democratic Party, describing the party as corrupt and attacking its escalating legal efforts to challenge his ballot access and its refusal to allow a debate between Mr. Kennedy and Mr. Biden.

“The Democrat political machine is pulling out every trick in the book to stop our huge momentum,” the email said. “With endless resources, establishment Democrats want to stop a debate between Robert F. Kennedy Jr. and Biden. They are using a vast network of shadowy dark money groups and vicious attorneys to keep Kennedy-Shanahan ticket off state ballots and spread malicious smears.”

Dr. Levitsky and Dr. Berman both noted that it was rare, in a democratic country, for a politician to explicitly reject democratic norms. It is more common for them to try to create a cloud of doubt so voters struggle to know what is true.

“Those who engage in misinformation about democracy, those who muddy the waters about what is and isn’t democratic, are complicit in the assault on our democracy,” Dr. Levitsky said. “The kind of behavior that sustains a democracy hasn’t changed over time.”