With some Democrats unsure of a Biden candidacy, what are the chances of a brokered convention?

Dogged by low approval ratings and concerns about his age, health and mental acuity, U.S. President Joe Biden continues to face concerns from some Democrats about his electability for a second term in office.

These concerns were more recently fuelled by a damning report from a U.S Justice Department special counsel over his handling of classified documents. The report referred to Biden as a "well-meaning, elderly man with a poor memory" who also suffered from  "diminished faculties." And for some Democrats, his subsequent news conference didn't help allay those fears.

Those fears have also sparked much speculation about whether Biden could be replaced as the party's nominee at this point. He is facing little opposition in the primary contest, meaning he is almost guaranteed to have secured the majority of delegates needed headed into the Chicago convention in August.

But the idea of a possible replacement is gaining more traction following a New York Times audio essay by journalist Ezra Klein. The essay, titled "Democrats Have a Better Option Than Biden," suggests that party leaders need to convince Biden to step aside and allow for a brokered convention.

That would mean, with Biden no longer a candidate, Democratic delegates at the convention would choose a new leader to face off against the Republican nominee, who at this point will almost certainly be former president Donald Trump.

But just how likely will this happen? Not very, say political observers.

Is it too late to compete against Biden in the primaries?

Those hoping some latecomer Democrat could still swoop in and challenge Biden in the primaries are out of luck, says Caitlin Jewitt, an associate political science professor at Virginia Tech, whose focus includes U.S.presidential primaries and caucuses.

At this point in the race, the filing deadlines to become a candidate have passed in more than 80 per cent of the states.

That means "there is no mathematical way that another candidate can enter the primaries and secure a majority of delegates and become the nominee," she said.

What if Biden steps aside?

The delegates Biden racks up during the state primaries will cast their votes for him at the Chicago convention during what is essentially a state-by-state roll call. With Biden having run virtually unopposed and having attained the majority of delegates needed, this is when he would be officially declared the party's presidential candidate.

If Biden decided at the convention that for whatever reason, he is not going to run in this year's election, then, yes, Klein's idea of a brokered convention would come into play.

"They basically do multiple ballots at the convention until a candidate gets 50 per cent plus one," Jewitt said.

Names that have been bandied about include Vice-President Kamala Harris, California Gov. Gavin Newsom, Michigan Gov. Gretchen Whitmer and New Jersey Sen. Cory Booker.

If Biden decided to end his campaign today, the party's nominee would still have to be decided by ballot at the convention because, with nominations open only in a handful of states, there are not enough delegates in those states for any new candidate to get the majority needed.

Jewitt, however, believes that with no obvious successor to Biden, that situation would be "utter chaos."

The significant challenge, she said, would be the search for a candidate who can beat Trump, who also unifies the moderate and progressive wings of the party and appeals to various demographic groups.

"And that is going to be the Democratic Party basically fighting itself three months before the general election," she said. "There just is no obvious candidate."

But, really, what's the likelihood Biden would drop out?

Barring some debilitating medical episode, it's almost a certainty that Biden will resist calls to step aside.

"He's very ambitious. This was a goal for a very long time," Jewitt said. "He's run for president several times. No one gets to the office of president and says, 'Oh, actually, I'll give it up.'"

Peter Loge, director and associate professor of George Washington University's School of Media and Public Affairs, compared Biden's presidential ambitions to "the guy who spent all night fighting for a seat at the bar."

"He's not going home after one beer," he said.

"There's no politician in America who says: 'You know what? I could be the Democratic nominee. I could be president for another four years. That's a sweet gig. You know what? I think I'd rather watch television.'"

Could the delegates just choose someone else?

The delegates that Biden wins during the primaries, while pledged to him, are not legally bound to him.

The Delegate Selection Rules for 2024 say the pledged delegates must "in all good conscience reflect the sentiments of those who elected them."

The term "in all good conscience " is the out, according to Elaine Kamarck, author of Primary Politics: Everything You Need to Know about How America Nominates Its Presidential Candidates.

That means delegates could support someone else if they had very serious concerns about Biden, whether he had a significant medical issue or, for example, a major scandal emerged.

"But it would take something pretty extreme for his delegates to desert him," Kamarck said. "The delegates are not going to turn against Joe Biden at the convention.

"It's only if there's some dramatic event that happens that then Joe Biden takes himself out or God takes him out. But other than that, it's not going to happen."

Jewitt added that when Biden wins these state primaries, it's his campaign that selects the delegates that go to the convention, which include donors, people who work on the campaign and Democratic Party county chairpersons.

"These are people who are supporting Biden. They are not going to go into the convention and vote for someone else," she said.

"They're very supportive and loyal. It would have to be a pretty major issue, pre-convention, to get a majority to essentially defect from him."

However, Jewitt did say that if in April or May, Biden continues to be plagued in the media about issues concerning his memory and his age, and his polling numbers continue to crater, then it's possible there could be a move from influential Democratic elites to start talking to him about departing the campaign.

"But I don't think it comes without [Biden's] agreement," she said. "I don't think they push away an incumbent president who didn't have any competition in the primaries and go with someone else."