WASHINGTON (AP) — Former Sen. Joe Lieberman, the Connecticut Democrat-turned-Independent long known for his centrist views, voted for Joe Biden in 2020. But as Biden's reelection campaign begins, Lieberman is preparing to recruit a third-party candidate capable of defeating the Democratic president.

"Centrists and moderates feel that he's governed more from the left than they hoped," Lieberman, a leader of the group, No Labels, said of Biden in an interview. "He hasn't been able to be the unifier that he promised to be."

Biden's political challenges are not confined to voters in the middle. In the days since he formally launched his 2024 campaign, key members of the sprawling political coalition that lifted him over former President Donald Trump in 2020 are far from excited about the prospect of four more years. That underscores the test confronting Biden as he aims to motivate the coalition of African Americans, Latinos, young people, suburban voters and independents to show up for him again.

John Paul Mejia, the 20-year-old spokesman for the progressive Sunrise Movement, says Biden has simply not done enough to ensure the young voters who rallied behind him in 2020 would do so again.

"Young people are starving for more," Mejia said, pointing to Biden's recent decision to approve two controversial fossil fuel projects in Alaska. "Biden has to demonstrate the extent to which he's willing to be a fighter. We've seen this sort of two-step on the promises he made to young people."

Biden has also struggled to fulfill key promises to Black voters, perhaps the most loyal group in his political base. While he tapped Ketanji Brown Jackson to become the first Black woman on the Supreme Court, he has been unable to follow through on pledges to protect voting rights against a wave of Republican-backed restrictions or enact policing reform to help stop violence against people of color at the hands of law enforcement.

"There's work to be done," said Rep. Jasmine Crockett, D-Texas, a 42-year-old African American former civil rights attorney who joined Congress in January. "I'm not going to sugar coat it."

Crockett recalled the palpable excitement among the Black community for Barack Obama's reelection. With Biden, there's "a number of people who are concerned and scared" largely because of his age, while others are "indifferent and waiting," despite what she described as Biden's overall strong record of achievement.

Nearly 18 months before Election Day 2024, however, it's unclear how much this lack of enthusiasm will weigh on Biden's reelection prospects. For all the concern, no high-profile Democratic primary challengers have emerged, and none are expected to. To date, only progressive author Marianne Williamson and anti-vaccine activist Robert F. Kennedy Jr. are mounting symbolic challenges to Biden, who has the official support of the Democratic National Committee.

Vermont Sen. Bernie Sanders, Biden's chief rival in the 2020 primary, told The Associated Press just hours after Biden announced that he was endorsing the president and encouraged other progressive leaders to do so as well.

"I intend to do everything I can to see that he is reelected," Sanders said in an interview.

Instead of excitement for the 80-year-old president's reelection, leaders from key factions in Biden's coalition report a serious sense of duty — and fear of the alternative. Trump is currently considered the favorite to claim the Republican presidential nomination, although he's facing opposition from a half dozen rivals.

"It would be a mistake to underestimate Trump or whoever the Republican candidate might be," Sanders said. "There's a lot of discontent in this country. There's a lot of anger in this country."

Indeed, 74% of U.S. adults believe the country is headed in the wrong direction, according to an AP-NORC poll conducted a week before Biden's announcement.

The poll found that only about half of Democrats think Biden should run again. Despite their reluctance, 81% of Democrats said they would probably support Biden in a general election if he is the nominee. That includes 41% who said they definitely would and 40% who said they probably would.

The warning signs in the Biden coalition are clear.

Just 41% of Black adults want the Democratic president to run again, and only 55% said they are likely to support him in the general election if he is the nominee. Among Latinos, only 27% want Biden to run again in 2024 and 43% said they would definitely or probably support him.

Younger Democrats also remain a reluctant part of Biden's coalition, the AP-NORC poll shows.

Just 25% of those under age 45 said they would definitely support Biden in a general election, compared with 56% of older Democrats.

Still, an additional 51% of younger Democrats say they would probably vote for Biden in a 2024 general election.

Meanwhile, just 14% of independents — adults who don't lean toward either party, who represent a small percentage of the American electorate — want Biden to run again. And only 24% said they'd support him in the general election if he is the Democratic nominee.

Biden's team dismisses the numbers, yet acknowledges that in a party as diverse as the Democrats, some may have other preferred candidates for president. It's just that none of those other people can win, they say, adding that while Biden might not be someone's first choice, he's often everyone's second.

They cite one of Biden's favorite political aphorisms: "Don't judge me against the Almighty, judge me against the alternative."

Their confidence is grounded in Biden's experience in 2020, when he was written off by much of the party, until it unified around him at the onset of the COVID-19 pandemic as a consensus candidate best positioned to defeat Trump. While Biden aides are expecting a rematch with Trump, he intends to cast all Republicans as embracing Trump-ism, both as a hedge in case another GOP candidate emerges as the party's standard-bearer and to broadly define the Republicans in an effort to help down-ballot Democrats.

Meanwhile, Biden himself has been open about there being more to do — it's in his campaign rallying cry "finish the job" — and his aides believe it is essential for him to highlight what else he wants to do with another term in office, believing that presidents who solely focus on their records lose reelection.

Biden has begun holding events to highlight popular components of his agenda that got left on the cutting room floor during the Democrats' legislative blitz over the last two years. Last week, he held a Rose Garden gathering to showcase his efforts to boost the affordability and quality of child and long-term care. And he's pushing for tougher gun laws after recent high-profile shootings and to write into law a national right to abortion.

Both are proposals his aides believe have the backing of most Americans — and are of particular importance to the Democratic coalition — but are unlikely to pass unless Democrats also win significant congressional majorities.

Aiming to address the intra-party concerns, Biden's campaign on Monday released a new ad it said was targeted at the "Biden coalition" of suburban women, Black and Latino voters, and swing and independent voters, that both lists what he's gotten done in office and what more he wants to do.

In the White House, Biden advisers, particularly chiefs of staff Ron Klain and now Jeff Zients, have kept close ties to grassroots groups across the Democratic firmament. He just secured an endorsement for reelection from the progressive group MoveOn, which said, "This moment requires urgency to solidify behind President Biden and show unified resolve to defeat MAGA and build on the progress of the last two years."

At a donor event in Washington on Friday, Biden's efforts to highlight his support from all swaths of the party were on display, with young progressive Rep. Maxwell Frost joining more establishment lawmakers like Sens. Chris Coons and Bob Casey. Investor Tom Steyer, who was among the Democrats who challenged Biden in 2020, also attended.

Allies said one key reason why the president selected Julie Chavez Rodriguez as his campaign manager was her ability to maintain close ties with a wide swath of the Democratic coalition during her time as White House director of intergovernmental affairs.

"This is not a time to be complacent," Biden said in his announcement video as he vowed to fight for freedom and warned of MAGA extremists and others who support banning abortion and books.

Meanwhile, Lieberman said he would likely soon begin interviewing potential candidates for No Label's third-party alternative to Biden and the eventual Republican nominee.

Already, No Labels has secured a spot on the presidential ballot in four states, including swing states Arizona and Colorado. Lieberman noted that the group would not field a candidate if polling suggested the so-called unity ticket does not have a viable path to the presidency.

"If No Labels does not run a bipartisan unity ticket, and the two candidates are Trump and Biden, to me, it's an easy choice," Lieberman said. "I will vote for Biden."

___

Peoples reported from New York. AP writer Hannah Fingerhut contributed.