Biden and Trump seem set for 2024 rematch -- why do their bases say they want anyone else?

Joe Biden and Donald Trump have been headed for another face-off since the day Trump lost to Biden in 2020 -- but voters say they are upset with the direction of the country and just as ambivalent about having either Biden or Trump lead their political parties in two years, adding an unusual level of uncertainty to what could be an historic 2024 contest.

A New York Times/Siena College poll earlier this month showed abysmal numbers for both leaders: Biden's job approval scraped 33%, a new nadir, and 64% of Democrats surveyed said they wanted a different nominee in 2024. Meanwhile, 51% of Republicans said they wanted someone other than Trump to be their standard-bearer in the next presidential election -- and despite Biden's unsteady footing, Trump still narrowly trailed him in a hypothetical head-to-head.

Such stark numbers only supercharged speculation, among politicos, over whether either of the two will be on the ballot come 2024. How unusual would it for them to run against one another again? If not them, then who? And what can change between now and then?

"When you have such a sour, negative political environment, voters in general are looking for change," said GOP pollster Robert Blizzard. "They're looking for new voices, new people."

The underlying reasons for this can be contradictory, given voters' political differences. There is concern about the economy and rising inflation, about the persistence of the coronavirus, about crime and gun violence -- including the habitual spasms of mass shootings -- and about abortions, LGBTQ rights and more.

Gallup's polling on how "satisfied" Americans are has consistently declined since the mid-2000s -- but it has shown ever-sharper dissatisfaction since 2021. The most recent survey, in June, reported 87% dissatisfaction.

As those numbers refuse to budge -- and, in particular, as voters increasingly focus on historically high inflation despite other good economic news -- Biden's approval rating has crumbled.

Steve Phillips, a progressive Democratic donor, said there was another factor influencing Biden's intraparty weakness: Democrats want him to be more forceful in advocating for the base's priorities.

In response, Biden and his administration have touted a range of executive actions he has taken but stressed that he is limited by Democrats' fragile majority in Congress. Often, Biden will urge voters to elect more Democrats so he can do more.

Phillips, the donor, sees it another way.

"There's 45-47% of people in the country who are going to hate Biden regardless. And then the worst is: What about those who elected him? And that's where the disappointment comes in. And there's such a reluctance to tackle the fights that are coming with the same intensity that they are coming. That's what I think is responsible for the low poll numbers," he said.

Still, Trump hasn't seemed to reap many benefits from the drop in Biden's support.

The same Times/Siena poll showing Biden only winning the approval of a third of all voters also showed that 92% of Democrats would back him if he faces off against Trump in a general election, where he would be expected -- in this survey -- to narrowly triumph.

Biden insists he'll run again if he's healthy. In an impassioned exchange with ABC News earlier this month, he said, "They [Democrats] want me to run." Pressed on this, he noted that "92% said if I did, they'd vote for me."

Still, his anemic approval ratings and advanced age -- cited by a third of Democrats in the Times/Siena poll as the reason they wanted another nominee -- have fueled a rumor mill over his second-term ambitions at the same time that other politicians have jockeyed for a bigger spotlight.

Observers say the potential 2024 short-list includes past candidates like Vice President Kamala Harris, Sens. Bernie Sanders (I-Vt.) and Elizabeth Warren (D-Mass.) and Transportation Secretary Pete Buttigieg.

Democratic Govs. Roy Cooper of North Carolina, Gavin Newsom of California, J.B. Pritzker of Illinois and Michigan's Gretchen Whitmer were also repeatedly mentioned by over a half-dozen Democratic aides who spoke to ABC News.

"I think there is a lot of people who could very quickly step into the spotlight who are qualified, who are dynamic and who I think could capture the public's imagination," said strategist Jon Reinish.

Some of the would-be candidates have, according to reports, privately acknowledged the possibility of 2024.

The Washington Post reported that it obtained a memo earlier this year written by a Sanders' campaign adviser that Sanders would consider a third White House bid if Biden didn't run in 2024.

Others have conspicuously swatted away the idea that they're waiting in the wings.

During an earlier interview with ABC News, Newsom insisted he had no White House ambitions -- which he reiterated while in Washington this month to accept an award on education. He said then that he supported Biden being on the ticket in 2024.

But Newsom -- like Govs. Pritzker and Whitmer -- has also seized on certain issues. All three have seen their profiles grow as a result. Pritzker, who recently made a trip to New Hampshire, spoke bluntly about why he supported gun control in the wake of a Fourth of July parade massacre in his state.

Meanwhile Whitmer has emerged as a forceful Democratic defender of abortion access and Newsom, despite playing down the 2024 possibilities, this month ran an ad in Florida berating Republican Gov. Ron DeSantis -- and casting himself as a culture warrior in the process.

Many party experts said that it was Harris who would start in a particularly strong position.

"Whereas you may hear people making waves or putting their toe in the water, there's always the presumption and the courtesy that … we'll wait to see what the current vice president is going to do," said one Democrat with ties to the White House.

Some Democrats chalked that activity up to just laying the groundwork if Biden were to pass on 2024 -- but observers said the candidates could be getting more emboldened as Biden's footing worsens.

"I think that the poll numbers, the whispers, certainly I think do motivate people to float trial balloons," said Phillips, the donor.

Across the aisle, Republican rumors over 2024 are flying just as fast.

Trump has openly teased a forthcoming comeback bid -- telling New York magazine in an interview this month that "in my own mind, I've already made that decision" and that he was only debating the timing of his announcement.

Still, he would be running as the party's most recent presidential loser -- and one who faces not only intense scrutiny over his actions around last year's Capitol riot but also a number of legal problems, including investigations in Georgia and New York. (He denies all wrongdoing and has cast the House Jan. 6 committee as politically motivated.)

Some critics also note that, like Biden, he has been dogged by questions about his advancing age and acuity.

On top of that, Trump seems fixated on his loss to Biden -- a focus that some experts say keeps him from talking about issues like inflation that are currently motivating voters.

While Trump remains the de facto GOP leader and party kingmaker, offering or withholding a powerful endorsement in down-ballot races across the country, strategists are forecasting a crowded field for the 2024 nomination.

"By focusing on 2020 all the time and trying to litigate that election, he's not presenting a positive vision for the future. And I think that there are some other Republican candidates out there who are making it pretty clear that they want to run in '24 and that they have ideas as to where America should go and they're not afraid to run, even if Trump is in the race," said Bob Heckman, a veteran of several GOP presidential campaigns.

The list of other would-be 2024 candidates amounts to a who's-who of Republican leaders, including Trump's own Vice President Mike Pence, former Secretary of State Mike Pompeo, former U.N. Ambassador Nikki Haley, Florida's Gov. DeSantis and Sens. Tom Cotton of Arkansas, Ted Cruz of Texas, Josh Hawley of Missouri and Rick Scott of Florida.

Vocal Trump detractors like Maryland's Republican Gov. Larry Hogan -- who sent nearly hourly tweets about a recent trip to New Hampshire -- are also being floated.

Several of those politicians are endorsing their candidates in the midterms, even when it conflicts with Trump, and traveling to critical primary states.

And while many of them may stay out of a primary should Trump run, laying the groundwork early could be critical in case he doesn't.

"Anyone who is thinking about running for president will realize that this could be their last best shot. Because if they don't run, and another Republican wins, they're effectively sidelined for the next decade," said Alex Conant, a top aide on Sen. Marco Rubio's (R-Fla.) 2016 presidential campaign. "If a Republican wins in 2024, the next time there'll be an open White House is 2032."

But timing is a delicate dance in the Trump-dominated GOP. While the former president is not anticipated to clear the field if he runs, being the first opposing primary candidate out of the gate could engender brutal attacks -- a repeat of Trump's approach to his 2016 opponents.

"I think there's a recognition and a degree of respect for Trump's political power of waiting. They have no choice. Those who step out too early can get slapped down really easy," said former Michigan Republican Party Chair Saul Anuzis.

Should Biden and Trump both run and win their respective nominations -- as many expect -- strategists of both parties are anticipating a highly unusual election.

A rematch between a current and former president, both of whom are facing popularity issues within their own party, would be virtually unheard of.

Historian Mark Updegrove said the closest comparison is President Grover Cleveland, who served from 1885 to 1889 before losing to Benjamin Harrison, only to reclaim the White House four years later.

But even that is not an apples-to-apples comparison.

"That's the closest thing we come to this. But the circumstances here are highly unusual for so many reasons, not the least of which is you'd have to septuagenarians right now who are considering this race, and by the time the election comes around, Joe Biden will be 82 years old. So age becomes a factor in this as well as all the other unusual aspects of the matchup," Updegrove said.

That being said, Updegrove noted that if current economic conditions continue, Trump has a wide opening to go on the offense given rampant inflation -- but he may be undercutting himself by his singular focus on the 2020 election.

"Americans are going to be tired of it ... And if he continues to harp on this message that something was taken from him, that election was stolen from him, I think it's going to hurt," Updegrove said. "I think the smart play would be to talk up what he could do to rejuvenate a foundering economy. That, to my mind, is Joe Biden's true Achilles heel."

Operatives, of course, warn against reading the tea leaves in the summer of 2022. The distance to the 2024 race is essentially a political lifetime. Trump himself proved that: The real estate mogul and reality TV host was on almost nobody's radar as a sincere candidate in summer 2014.

"It's good not to chisel your long-term plans in politics into rock," said Jared Leopold, a former top staffer at the Democratic Governors Association. "It's better left in pencil."