Joe Biden conceded that his age is a "legitimate" concern for voters during an event with donors Wednesday.

The oldest president in American history told supporters that his unsolicited decision to seek re-election wasn't "automatic."

"It wasn’t an automatic decision about running again,” Biden said. “Not because I didn’t think there was more to do, but because I thought to myself…four more years means six more years. It’s a long time.”

"It’s a legitimate thing to raise the question of age," Biden said.

Biden admits it

Biden is pursuing re-election despite widespread doubts about his age and a lack of enthusiasm among his own voters.  A longtime adviser warned Biden the upcoming campaign would be "tough," Biden told donors in New York.

“It could be a pretty ugly campaign, maybe, coming on,” Biden said.

Biden has sought to spin the issue by saying his age has brought wisdom, but that "wisdom" hasn't produced the kind of results that win public approval.

A brutal ABC/Washington Post poll found just 36 percent approving of Biden's performance. In a head-to-head with chief rival Donald Trump, Biden loses by 7 points.

Voters are not concerned about age with Trump like they are with Biden: just 44 percent see Trump as too old compared to 68 percent for Biden. Even 48 percent of Democrats said Biden was too old.

Trump fears

Unable to defend Biden's record or his fitness to serve, Democrats are running with alarmist messaging about "democracy" -- his campaign launch video invoked imagery from January 6th -- and the supposed existential threat posed by Trump, who is the strong favorite to be the Republican nominee.

The Democratic party seems to be preparing for a coronation, with no debates planned and no serious challengers -- at least from within the party establishment -- willing to take Biden on, as of yet.

While Democratic party elites embrace Biden as the least bad option to defeat Trump, some on the left are growing worried that Biden won't pull it off.

The country may have received a foretaste of liberal panic this week with the furious backlash to Trump's CNN town hall, which leftists bitterly compared to a MAGA rally.

The enthusiasm of the crowd and the energetic performance of 76-year-old Trump made it impossible to mistake for a Biden event.