But then the CBS "Late Show" host dove right into jokes that were impossible for any political satirist to resist.

"I think that Biden debates as well as Abraham Lincoln -- if you dug him up right now," Colbert said this week.

He had company. Jon Stewart, Seth Meyers and Jimmy Fallon have all found fodder in Biden's stumbling, slack-jawed performance and in the Democrats' internal debate over whether the president should drop his campaign for a second term.

Late-night comics have skewered Biden's Republican opponent, Donald Trump, for years. Some have made no secret that their feelings were not just professional: Colbert moderated a panel discussion between Biden and former presidents Barack Obama and Bill Clinton at a Manhattan fundraiser in March, and ABC's Jimmy Kimmel held court at a Biden Hollywood event last month.

Yet to think they would have ignored Biden's troubles was naive, says Robert Thompson, a scholar of TV and its history.

"The idea that late-night comedy has been another mouthpiece for the Democratic party is simply not true, because comedy cannot afford to do that," said Thompson, director of Syracuse University's Bleier Center for Television and Popular Culture. "The job is that you've got to make fun of the people in power."

A week of pointed comedy

Although Stewart hosted a live version of "The Daily Show" on Comedy Central immediately following the June 27 debate, most of the comedic response has come this week because of vacation schedules.

In his first monologue back on Monday, Colbert made it clear that he believed Biden has been a great president. He referenced his appearance at the fundraiser, saying Biden seemed "ancient but cogent" that night. When Colbert showed a news report saying Biden had told fellow Democrats that he was fine, it was "just my brain," the camera cut to a shot of the comic lying prone on the floor.

"Who am I to recommend" what Biden should do? Colbert asked rhetorically. "I don't know what's going on in Joe Biden's brain -- something I apparently have in common with Joe Biden."

He dismissed the early explanation that Biden had a "bad episode" during the debate. "When 'Grey's Anatomy' did a musical, that was a bad episode," he said. 'This took a year off my life."

While Colbert hasn't pulled punches, "it looked to me like he was in some pain having to do it," said Bill Carter, author of "The Late Shift" and a writer for LateNighter.com.

The closest Colbert came to offering advice was when he said that Biden seemed caught between two virtues -- perseverance and self-sacrifice.

"Self-sacrifice takes a particular kind of courage," he said. "That is a courage that I believe Joe Biden is capable of. I believe he's a good enough man. He's a good enough president to put the needs of the country ahead of the needs of his ego. And however painful that might be, it is possible that handing leadership to a younger generation is the right thing for the greater goodest."

A heartfelt statement -- with a zinger at the end. The last word is a reference to a gaffe in Biden's interview with George Stephanopoulos.

A change that probably buoys Donald Trump

Kimmel, who has been the subject of bitter attacks from Trump and has given them right back, is off this summer. He has not weighed in on Biden on his X account.

"I imagine he's happy to be on vacation," Carter said.

No doubt the change in tone is being relished by Trump, who has faced a "drumbeat of mockery" on late-night television, Carter said. His tiff with Kimmel and sour comments about "Saturday Night Live" are evidence of a thin skin. "SNL," like Kimmel, is off for the summer.

Stewart has taken exception to the way some Biden supporters have groused that more attention should have been focused on things Trump said during the debate. He pointed out on "The Daily Show" that Trump has been criticized by comics "every night for 10 years."

"We expected him to be f----- crazy," Stewart said. "But Biden's performance and inability to articulate at times was stunning. I couldn't believe what I was watching."

He said on his podcast, "The Weekly Show," on Thursday that Biden's team has been dishonest about the president's condition. Earlier on "The Daily Show," he called for a more open conversation.

"Do you understand the opportunity here?" Stewart said. "Do you have any idea how thirsty Americans are for any kind of inspiration or leadership and a release from this choice of a megalomaniac and a suffocating gerontocracy?"

On his NBC show, Meyers said that when he watched the debate, "I tried turning on the captions, but that just made it worse." He also mocked Biden's promise to get more rest.

"Your plan to calm fears about his age is an earlier bedtime?" Meyers said. "Are you hoping we'll forget he's 81 if you treat him like he's 5 1/2?"

Late-night comics may not have the television audience that they used to, but they arguably still have a disproportionate influence in the public discourse, Syracuse's Thompson says. In the case of the Biden jokes, he says, they're "influential because it's the last place you might have expected to see them."

Particularly for a younger generation, what the hosts say is often more likely to be experienced through video clips found online or shared on socials the next day. That was the case this week on "Morning Joe," which replayed a routine by Jimmy Fallon on the "Tonight" show that referenced an interview with former House Speaker Nancy Pelosi on "Morning Joe" the day before.

Fallon has kept his jokes mostly light, as he did Thursday night: "Biden," he said, "hasn't seen so many people jump ship since he vacationed on the Titanic."

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David Bauder writes about media for the AP. Follow him at http://twitter.com/dbauder.