There is some fascinating reporting from CNN's Edward-Isaac Dovere about the increasing levels of angst top Democrats are expressing about President Joe Biden's reelection campaign.

Dovere refers to worried conversations among Democrats and donors, contrary to all the public evidence, that maybe Biden won't end up running for reelection.

"They feel like time is already running out and that the lack of the more robust campaign activity they want to see is a sign that his heart isn't really in it," Dovere writes.

Here's a longer excerpt:

In a race that many expect will likely come down to a few hundred thousand votes in a few states, the doubters argue that every day without a packed schedule on the stump will prove to voters that Biden's age is as big a worry as they believe it is. Or that the president and people around him aren't taking the threat of losing to Donald Trump or another Republican seriously enough, and they're setting up for Election Night next year to be 2016 déjà vu.

"If Trump wins next November and everyone says, 'How did that happen,' one of the questions will be: what was the Biden campaign doing in the summer of 2023?" said a person who worked in a senior role on Biden's 2020 campaign.

Read the entire report.

The Biden world retort: This again?

On "Inside Politics" on Thursday, CNN's Dana Bash asked Dovere for his takeaway on how much people currently inside Biden world privately agree with the concerns coming from outside.

"Inside Biden world, the real circle of people around the president, they don't agree with this at all," he said. "What they would say is, 'How many times do we have to go through this? How many times do people have to doubt Joe Biden and say he can't win an election? ... And then at the end of the day, he won the primaries, he won the nomination, he won the election in 2020.'"

Dovere also quotes Jim Messina, Barack Obama's 2012 presidential reelection campaign manager, who has been privately advising Biden's team.

At this point in that cycle, Obama's campaign was much more fully formed, according to Dovere, who writes of Biden's reelection effort:

The headquarters in Wilmington discussed to be open by mid-July still isn't. No staff is currently on the ground in competitive states, and names of potential hires have only started to be collected for review by the president and top advisers.

The dozen people who are working for Biden-Harris 2024 full-time are mostly camped out at desks in the Democratic National Committee near Capitol Hill in Washington, with some griping about the delays in hiring staff and others still grumbling about how long it took to get on the payroll themselves. There is still no campaign finance director.

Obama's reelection, remembered

Obama may have had more infrastructure in place, but that doesn't mean his 2012 effort was worry free. It's hard to believe it now -- more than a decade later -- but Obama's primary journey in 2012, while a sure thing and a cakewalk, was also beset by frustrations.

For instance, Gallup released a poll before the 2010 midterm election suggesting that more than a third of Democrats and Democratic-leaning adults would back his secretary of state, Hillary Clinton, if she challenged him for the nomination. She obviously never did.

Obama was extremely weakened after that 2010 midterm, suffering what he called a "shellacking," when Republicans claimed a much larger House majority than the barely-there edge Republicans currently enjoy in the House.

Where Biden and Obama are about equal

In the summer of 2011, although it was not reported publicly at the time, Sen. Bernie Sanders seriously considered challenging Obama, according to subsequent reporting by Dovere for The Atlantic. Then-Senate Majority Leader Harry Reid intervened to talk Sanders down, and Messina told Dovere that the prospect of a Sanders challenge had Obama's campaign team "absolutely panicked."

At this point in Obama's presidency, the summer of 2011, his approval rating among all adults was 44%, just about tied with Biden's Gallup approval rating of 43% at the end of June.

Obama's approval rating among Democrats at this point in his presidency was 79%, which is about the same as Biden's approval rating among Democrats today -- 82% in the Gallup polling from the end of June. But Obama had slightly more support among Republicans, which may have something to do with the ever-more-partisan national political environment.

During the actual primary, Obama kept suffering embarrassments

A prison inmate got 40% of the Democratic vote in the West Virginia primary in 2012. CNN's Jake Tapper wrote about it for ABC News at the time and noted that Sen. Joe Manchin would not say who he voted for -- Obama or inmate Keith Judd -- according to one report.

In other red states, Obama also struggled in the primaries, getting less than 60% in primaries in Kentucky and Arkansas.

These were not exactly contested races, and the fact that Obama didn't have a stronger showing is probably a reflection of who shows up to vote in a nationally uncontested Democratic primary when the real race that year was on the Republican side.

Republicans canceled some primaries in 2020

When the situation was reversed in 2020 and then-President Donald Trump faced some token challengers, Republicans simply canceled multiple primaries. South Carolina canceled its primary even though its former governor, Mark Sanford, was challenging Trump.

This year, it's another former South Carolina governor, Nikki Haley, and a sitting South Carolina senator, Tim Scott, who are running in the single digits in national primary polls.

Biden's top challenger so far is an outcast Kennedy

For Biden, his biggest challenger so far is Robert F. Kennedy Jr., whose campaign is driven by anti-vaccine conspiracy theories.

Yes, Kennedy is registering in polls -- more than 10% in many. But his out-of-the-mainstream views also mean he can't get the backing of his family members, much less be viewed as a viable Biden alternative.

For an idea of how much of a long shot Kennedy is, read this analysis from CNN's Harry Enten.

There's certainly nothing as dangerous to Biden as when Sen. Ted Kennedy tried to displace then-President Jimmy Carter in 1980, inarguably wounding Carter before he was trounced by Ronald Reagan.

There's also nothing like the spirited primary challenge by Pat Buchanan that wounded then-President George H.W. Bush's chances in 1992. Nor is there a serious independent bid that could feature in the general election, like Ross Perot's in '92. Bush ultimately lost the three-way race to Bill Clinton.

All of this suggests that while Democrats will continue to worry about Biden's age, his campaign structure, his unique ability to stumble over words and all of the ways Republicans attack him, he's a lock to be their nominee barring unforeseen events.