WILMINGTON, Del. (AP) — Leading progressives are pressuring President-elect Joe Biden to embrace their policy agenda even as more centrist Democrats argue such proposals prevented the party from retaking full control of Congress.

For now, much of the lobbying centers on who Biden should — or should not — appoint to key posts as he builds out the administration that will take office in January.

The left-leaning think tank Progressive Change Institute partnered with more than 40 activist groups and on Friday released a detailed list of 400 progressive policy experts they want Biden to bring on. That follows a separate effort from more than half a dozen progressive groups this week that signed letters urging the president-elect against naming anyone with ties to major corporate interests to key Cabinet posts.

“Now is absolutely the moment to push Biden to do what’s necessary to meet the moment," said David Segel, a former Rhode Island state representative and executive director of Demand Progress, which was among those signing the letters. "And that means a robust economic response, a robust health care response, a willingness to push back against concentrated corporate power that’s fomenting inequality. And he has a mandate to do all of that.”

The jockeying amounts to the opening round of what is likely to be a lengthy debate over the future of the Democratic Party. Some centrists have blamed losses in the House and a disappointing performance in the Senate on Republicans' ability to paint Democrats as having moved too far to the left.

That’s creating tension for a party that should be basking in the glow of defeating an incumbent president for the first time in nearly 30 years.

"We’re a big family. There’s lots of different parts to the family,” said Mitch Landrieu, the former Democratic mayor of New Orleans who has a reputation as a political centrist. “It’s a welcome discussion because the country is changing dramatically, and we have to think of how to navigate into the future.”

Much of the focus will be on how Biden fills out his administration. In a letter earlier this week, top progressive groups asked Biden to “decline to nominate or hire corporate executives, lobbyists, and prominent corporate consultants to serve in high office.”

They also said he should aggressively make appointments while Congress is not in session and employ the Vacancy Act, a 1998 law that allows for appointments to administration positions for more than 200 days without Senate approval.

Doing either would keep Senate Republicans from blocking Biden’s top choices — especially the most progressive ones whose nominations would face the toughest confirmation fights. Additionally, the groups sent a similar letter to Senate Democrats instructing them to hold Biden accountable to those demands.

Biden has promised to expand Obama administration ethics rules curbing lobbyist and corporate interests in government, a stark departure from the Trump administration's friendly relationship with large businesses. But he's also leaning on advisers with deep Washington experience and calling for bipartisanship and healing a divided nation — meaning his new administration could drift naturally toward the middle, steered there by his top choices for top positions.

Biden won the presidency by refusing to embrace his party's most liberal causes, government-funded health care under “Medicare for All” and the Green New Deal, a collection of proposals to drastically remake the economy to combat climate change. He moved to the left amid the coronavirus outbreak, though, and is now promising to revive the economy once the pandemic subsides by spending $2 trillion to create green jobs and prioritize infrastructure improvements that reduce emissions and work to curb climate change.

“We’re assuming that he wants to implement the agenda that he campaigned on and to implement that agenda he will need folks in his administration who have that commitment to getting things done for the public good,” said Stephanie Taylor, co-founder of the Progressive Change Institute. “If he has corporate lobbyists in his administration, it would derail his agenda.”

Lauren Maunus, legislative and advocacy manager for the Sunrise Movement — a youth, activist organization that promotes the Green New Deal — said Biden bested Trump by “embracing a Rooseveltian vision” that includes the most ambitious environmental plan in U.S. history.

Maunus, whose group helped compile the list of 400 experts recommended for the Biden administration and, separately, signed the letters to Biden and Senate Democrats, said it wasn't simply a matter of policy debate within the Democratic Party, but instead a case where many corporate and fossil fuel interests are trying to seize the mantle of political centrists to protect their financial interests.

“He was elected on this promise of being a climate president,” Maunus said of Biden. “We think it’s both popular and politically advantageous to lean into this role.”

Segel of Demand Progress noted that Biden failed to win Florida even as its voters approved gradually increasing the state's minimum wage to $15 an hour, arguing that Biden might have fared better there if he had more fully embraced progressive ideals.

The policy clashes will begin to take more defined shape as Biden makes more choices for his new administration. So far, he's made only one major one, tapping his longtime adviser Ron Klain as his chief of staff. Klain served as czar to the Obama administration's response to the 2014 Ebola outbreak in the U.S., and the pick was cheered by moderate and progressive Democrats alike.

Other picks almost certainly won't go as smoothly, but Landrieu said Biden, with his decades of experience in government, is uniquely positioned to listen to all of the perspectives, then choose how best to move the party forward.

“I think that he will find a way to help navigate what we now call tension between progressives who say, ‘I want to go further,’ and moderates who are saying, ‘I’ll go as far as I can go, but there’s limits and really what should we even be thinking about,’” Landrieu said. “Everybody’s got a role, and the president’s role is to decide.”