Could a Democrat Really Challenge Biden at This Point? Here’s What to Know.

The Democratic anxiety that has swirled around President Biden for over a year has kicked into overdrive in recent weeks, as his approval ratings have stayed stubbornly low and polls have shown the possibility of his losing to former President Donald J. Trump.

That anxiety has crystallized into one question, repeated like a drumbeat: Can’t some big-name Democrat challenge him? Someone more prominent than Marianne Williamson or Dean Phillips?

The answer: In theory, sure. In practice, the prospects are remote.

There are several reasons for that, most of which boil down to it being really hard to run a successful primary campaign against a sitting president. And doing so at this point, just two months before voting starts, wouldn’t be feasible anyhow.

Making things still more difficult for a would-be challenger is that Mr. Biden remains relatively popular among Democratic voters. According to a recent New York Times/Siena College poll, 79 percent of party voters in six battleground states somewhat or strongly approve of his performance, which doesn’t leave a lot of room for another Democrat.

“Logistically, it’s impossible,” said Tim Hogan, a Democratic strategist who has worked for Hillary Clinton and Amy Klobuchar. “Politically, it’s a suicide mission.”

Ballot deadlines are approaching, or past

To appear on each state’s primary ballot, candidates must submit paperwork along with, in many cases, a hefty filing fee and hundreds or even thousands of voter signatures.

The deadlines for those submissions have already passed in South Carolina and Nevada, the first two states on the Democratic calendar; in New Hampshire, which is holding an unsanctioned primary in January; and in Alabama and Arkansas.

Michigan, another early-voting state, released its list of candidates this month. By mid-December, the window to get added to the ballot there will have closed. The deadline is similar for California, which will account for more delegates than any other state; and for Arizona, Colorado, Louisiana, Maine, North Carolina, Oklahoma, Tennessee, Texas, Vermont and Virginia.

So even if a candidate entered the race tomorrow, they would be unable to get on the ballot in the first two primaries, and probably in a lot of others. It would be a tall order, for instance, to secure 26,000 signatures in California by its Dec. 15 deadline.

Pretty soon, defeating Mr. Biden goes from difficult to mathematically impossible.

Biden has an enormous financial advantage

Mr. Biden’s re-election campaign, the Democratic National Committee and a joint fund-raising committee said they raised a combined $71.3 million in the third quarter of this year. They reported having $90.5 million in cash on hand as of the end of September.

That would put any new candidate at a staggering disadvantage. Consider that on the Republican side, Mr. Trump alone announced a $45.5 million haul in the third quarter, and his leading rivals, Gov. Ron DeSantis of Florida and the former United Nations ambassador Nikki Haley, reported raising $15 million and $11 million.

Big-name politicians are thinking long term

Many voters looking for a savior candidate are, naturally, looking to people seen as rising stars in the Democratic Party — like Gov. Gavin Newsom of California, Gov. Gretchen Whitmer of Michigan or Gov. J.B. Pritzker of Illinois.

But rising stars generally want to maximize their chances at the right time.

“Ambitious candidates are risk-averse,” said Casey Dominguez, a professor of political science and international relations at the University of San Diego who studies primaries. “They don’t want to ruin their chances at a successful run for president by having an unsuccessful run for president, particularly one where you’re running against a sitting president, potentially dividing the party.”

Crucially, there is no precedent in the last 50 years for candidates to look to for a path.

Pat Buchanan, challenging an unpopular President George Bush in 1992, gave Mr. Bush an unexpectedly close call in New Hampshire but did not end up winning a single primary. Edward M. Kennedy, challenging an unpopular President Jimmy Carter in 1980, won 12 states and contested the nomination all the way to the Democratic convention, but did not come close to a majority.

“History tells a story,” said Barbara Norrander, an emeritus professor at the University of Arizona’s School of Government and Public Policy who studies presidential primaries. “Ted Kennedy versus Jimmy Carter 1980 is what you would look back at, and Kennedy had a lot of pluses going for him, but he wasn’t able to unseat Carter. So it’s highly unlikely that someone today could unseat an incumbent president.”

Democrats are worried about weakening Biden

The driving force behind many Democrats’ desire to jettison Mr. Biden is fear of another Trump presidency. But the same driving force is behind other Democrats’ desire to stick with him.

Mr. Biden’s vulnerabilities, including his age and low approval ratings, are very real. But the electoral advantages of incumbency, universal name recognition and an established campaign organization are real, too.

At this point, for a new candidate, “there’s just no way to build momentum and get the resources necessary,” Mr. Hogan said.

Potential challengers also have to weigh the possibility that a primary battle could weaken Mr. Biden in the general election, even if he overcame it. Though there is no consensus, some historians believe primary challenges hurt Mr. Bush and Mr. Carter in 1992 and 1980.

“Nobody wants to be the person that divided the party and helped to elect Donald Trump,” Professor Dominguez said.

There is no ‘generic Democrat’

Any challenger would come with their own weak points that would turn off one Democratic faction or another and be exploited by Republicans over the long months of a general-election campaign — a reality not necessarily captured by polls that show an unnamed Democratic candidate performing better than Mr. Biden.

“You can’t run a generic Democrat,” Mr. Hogan said. “You have to run a person.”

Take Representative Dean Phillips of Minnesota, who entered the race in October. After debuting around 7.5 percent in the FiveThirtyEight polling average, he quickly fell to about 4 percent.

That reality played out in 1968, the only time in modern history that an incumbent president was successfully challenged in his party’s primary.

Two challengers with substantial name recognition and support — Eugene McCarthy and Robert F. Kennedy — helped drive President Lyndon B. Johnson not to seek re-election. He announced his decision in March 1968, as the primaries were underway. That August, his vice president, Hubert Humphrey, won the nomination of an agonizingly divided Democratic Party.

Humphrey lost the general election with 191 electoral votes to Richard Nixon’s 301.

What happens if Biden can’t run?

To state the obvious, all of the considerations are what they are because Mr. Biden is running. If something were to change that — if he had a health crisis, for example — the party would be in a difficult situation.

If he withdrew just before or early in the primary season, voters would be limited to the other options already in the race. It is highly unlikely that ballot access deadlines, which are set by individual states and not by national party officials, would be reopened.

If he withdrew later in the primary season — after he had won enough delegates in early primaries that no candidate could surpass him — the nomination would be decided on the floor of the Democratic National Convention in August, where delegates have the final say in choosing a nominee. That would also be the case if he withdrew between the primaries and the convention.