Varying Treatment of Biden and Trump Puts Their Parties in Stark Relief

One of America’s political parties has a presidential candidate who is really old and showing it. The other has a presidential candidate who is a convicted felon, adjudicated sexual abuser, business fraudster and self-described aspiring dictator for a day. And also really old.

One of the parties is up in arms about its nominee and trying to figure out how to replace him at the last minute. The other is not.

The spectacle of the week since the nationally televised debate between President Biden and former President Donald J. Trump has thrown into sharp relief two political parties that agreed to be led by flawed putative nominees whose vulnerabilities have become even more painfully apparent just months before the election.

But the distinction of recent weeks has been striking. After Mr. Trump was found guilty of 34 felonies by a Manhattan jury in May — a verdict that came after civil judgments against him for personal and professional misdeeds — there was no significant groundswell within the Republican Party to force him out of the race in favor of a less-tainted candidate. Even though many Republican officeholders and strategists privately loathe him, they fell in line and made clear they would stick with him no matter how many scandals piled up.

Until last week, Democrats had also resigned themselves to a candidate many considered far from ideal. Mr. Biden and his allies had effectively squelched any internal dissent, forcing Democrats to stay quiet despite fears that his age would ultimately undercut his campaign. After last week’s debate showcased concerns about his mental sharpness, however, the conspiracy of silence was broken. Suddenly, a wide swath of Democrats concluded that he was no longer viable and mounted an effort to pressure him to step aside for a younger candidate.

“While Biden had the worst debate performance in all of presidential history, Trump’s was likely the second-worst,” said Jeffrey A. Engel, director of the Center for Presidential History at Southern Methodist University. “Yet we hear crickets from Republicans after their presumptive nominee was incoherent, rambling and utterly divorced from the truth. Oh, and also a convicted felon.”

The disparity says something important about the two major parties 248 years into the American experiment. Mr. Trump has come to thoroughly dominate his party in a way that no president has done in modern times, crushing internal opposition, punishing dissenters and enforcing loyalty even among those who have publicly declared him to be a danger.

Rather than be defensive over his many political liabilities, Mr. Trump has gone on offense, forcing his fellow Republicans to go along with his version of reality in which every accusation against him, even those proven in court, are all part of a wide-ranging conspiracy of persecution. He has turned shortcomings into power, at least among his own partisans.

“Republicans don’t see Trump’s convictions, his rhetoric nor his threats of retribution as moral or political infirmities,” said David Jolly, a former Republican congressman from Florida who has broken with his party over Mr. Trump. “Many see them as strengths. So we won’t see a parallel family conversation among Republicans that we are currently seeing among Democrats regarding President Biden’s age and questions of his fitness.”

That all of this is happening around the Fourth of July holiday serves as a reminder that the framers were not all that keen on political parties in the first place. Alexander Hamilton warned that parties, or “factions,” as they were called at the time, were “the most fatal disease” of popular governments. In his farewell address, George Washington said that the “common and continual mischiefs” of such factions made it imperative to “discourage and restrain” them.

Today’s parties live in radically different universes, interpreting the same fact set through radically different lenses. What used to be disqualifying no longer is. Mr. Trump was seen as such a threat by Democrats that they were willing to live with a nominee they knew could be risky. Mr. Trump has imposed his will on his party to the point that even rival candidates in the primaries did not criticize him for his alleged crimes or for trying to overturn an election.

Neither party should have been surprised by what would follow. It was eminently predictable that by the time voters began to cast ballots, Mr. Biden would have aged further and had more senior moments, and Mr. Trump would be found guilty of various acts of misconduct. Both parties knew the minefields they were heading into by sticking with Mr. Biden and Mr. Trump, and neither took enough action to head it off.

“We used to worry that partisanship would mean choosing the party over one’s country,” Mr. Engel said. “Now it appears to mean, again increasingly for both sides, choosing the man rather than the nation’s needs.”

Sarah Longwell, a Republican strategist and leading anti-Trump voice, said her party had succumbed to a demagogue. “The G.O.P. is a personality cult that turned itself over to Donald Trump a long time ago,” she said. “The Democrats are still a mostly functional political party, with a substantial chunk of members who believe that the stakes for beating Trump are existential and therefore worth a serious discussion about the best path forward.”

But Mr. Trump’s supporters argue that his issues are different from Mr. Biden’s. “The notion that these are equal, I just don’t see it,” said David Urban, a longtime Republican strategist who worked on past Trump campaigns. He compared the situation to a basketball star tearing an A.C.L. and being unable to play, as opposed to being obnoxious or insulting.

“You may not like Trump,” Mr. Urban said. “You may think he’s mean-spirited, you might not like his demeanor. You may think he’s crude, he’s rude, he’s brash. But you still think he can run the United States. Whereas with Biden, he’s not running anything.”

That Mr. Trump would seem capable compared with Mr. Biden is a matter of perspective. Mr. Biden, 81, at times during the debate confused his words, stared blankly and seemed lost. Mr. Trump, 78, whose mental fitness has been questioned by former advisers and who has appeared incoherent at times during public appearances in recent months, made statements during the debate that were hard to follow and in many cases flatly not true. But his voice was strong, he did not appear frail and instant polls showed that most viewers thought he did better than Mr. Biden.

Not that voters are particularly impressed with either man’s capacity. A post-debate poll by The New York Times and Siena College found that 74 percent of voters said Mr. Biden was too old for the job and that 42 percent said Mr. Trump was. The major difference is that many Democrats told pollsters they were ready to dump Mr. Biden (47 percent want another nominee), while Republicans were content to keep Mr. Trump (83 percent want him to remain their nominee).

In part, said Lynn Vavreck, a professor of American politics at U.C.L.A., that owes to the surprise factor of the debate. While voters knew Mr. Biden was aging, they were stunned to see it so pronounced on their living room screens. By comparison, she said, Mr. Trump’s rule-breaking has already been “baked in.” By the time he was convicted in New York, voters already knew he had been impeached twice and indicted four times and decided what they thought of those allegations.

“People had already factored the idea that he was guilty of these charges into their assessments of him,” said Dr. Vavreck, co-author of “Bitter End,” a book on the 2020 election. “No one had factored into assessments of Biden the idea that he was struggling as much as he revealed last week. And critically, this new information made people update their beliefs on his probability of success in November.”