WASHINGTON — Shortly after President Joe Biden announced Sunday that he would drop his reelection campaign, Democratic National Committee Chair Jaime Harrison had a message: There would be no automatic coronation for his replacement.

“In the coming days, the party will undertake a transparent and orderly process to move forward,” Harrison said in a statement. “This process will be governed by established rules and procedures of the party. Our delegates are prepared to take seriously their responsibility in swiftly delivering a candidate to the American people.”

The comment reflected the reality that while Vice President Kamala Harris is emerging as the prohibitive favorite to become the party’s nominee — backed already by Biden and many Democrats — it’s not so simple. And for now, the party isn’t offering many details on what happens next.

Harris has to formally secure the nomination from the around 4,700 Democratic convention delegates — including those pledged to Biden, as well as the elected officials, former presidents and other party elders known as superdelegates. She spent part of Sunday calling elected officials and delegates to solidify their support.

Biden won Democratic primaries in every state, and Harris was on the ticket as his running mate. His tapping her as his successor while bowing out of the race further strengthens her case, as does the endorsements of party heavyweights like South Carolina Rep. Jim Clyburn. Other top Democrats openly backed the vice president even before Biden abandoned his reelection bid, urging him to “pass the torch” to her in the wake of his dismal debate performance against Republican nominee Donald Trump last month.

“Folks will be weighing in and they should. I think we’re seeing a lot of coalescing behind the vice president,” said Rahna Epting, executive director of the progressive organization MoveOn. “And that’s important because, as we saw throughout the Biden debate fallout, there is momentum that can be built one way or the other, and it is important for us to build momentum toward unity.”

Ken Martin, president of the Association of State Democratic Committees, which represents the 57 parties in the states and territories, said Harris was the obvious choice: “Having served alongside President Biden, she is ready on day one as a candidate and as our next president.” She was also endorsed by the 1.75-million-member American Federation of Teachers union.

But Democratic rules state only that delegates “in all good conscience” vote for the candidate they were elected to represent, with no mechanism for defectors. And some in the party have endorsed an open nominating process.

There’s been active debate about how to proceed among lawmakers, major donors and former high-ranking officials of the Biden, Obama and Clinton administrations, a Democrat with deep ties to the Biden administration, said Sunday.

The person, who spoke on the condition of anonymity to discuss internal conversations, argued that Harris would benefit from a competitive mini-primary ahead of the Democratic convention, because it would help her seal her bonafides as a strong candidate and diminish criticism that she’s been undemocratically anointed. That’s a charge the Trump campaign has already sought to use against her, and could loom large in the battle for undecided voters in battleground states.

Such a scenario might leave Democrats heading into their national convention without a clear nominee, though, and perhaps choosing one via a series of potentially messy floor votes. That could mean top Democratic candidates looking to replace Biden resorting to visiting individual state delegations to lobby — a process unseen since 1960, when Johnson and John F. Kennedy jockeyed for support during that year’s Democratic convention in Los Angeles.

If that happened, in addition to Harris, many other leading Democrats could vie for the nomination, including the likes of California Gov. Gavin Newsom, Michigan Gov. Gretchen Whitmer, Pennsylvania Gov. Josh Shapiro and California Rep. Ro Khanna — though many of those said shortly after Biden’s announcement that they were formally endorsing Harris.

Inside the White House, meanwhile, there’s low expectation that Harris will get a serious challenge, according to a person familiar with deliberations who requested anonymity to discuss the private conversations.

Others who have been mentioned as viable contenders — including Shapiro and North Carolina Gov. Roy Cooper — have also both endorsed Harris and would seem unlikely to run in light of Biden’s backing her, and the expected fundraising advantage she would hold over anyone who’d enter the field.

Further complicating matters is the fact that the DNC had planned to hold a virtual roll call to choose its nominee ahead of the convention, in order to meet Ohio ballot eligibility rules. That state’s original deadline ballot deadline was Aug. 7, and though the Legislature has since approved a law nullifying that, it doesn’t take effect until Sept. 1.

Some Democrats fear a host of GOP legal challenges, including New York Rep. Alexandria Ocasio-Cortez, who had defended Biden staying in the race by arguing that replacing him might trigger “a presidential election being decided by Clarence Thomas and the Supreme Court” — like what happened during the 2000 presidential election and the disputed recount in Florida.

At this week’s conventions rules committee meeting, members could establish virtual roll call rules and a process to nominate Harris. But they could also create a more open process for choosing a nominee, according to a person familiar with the process on condition of anonymity to discuss internal deliberations.

“Here in Chicago, our mission remains the same. During the convention, we will have an opportunity to show the country and the world who Democrats are and what we stand for,” Minyon Moore, chair of the Democratic convention, said in a statement.

Harrison, the DNC chair, refrained from endorsing Harris in a statement, saying only, “In short order, the American people will hear from the Democratic Party on next steps and the path forward for the nomination process.”