Joe Biden just dropped out. What happens next?

President Joe Biden thrust his party into virtually unprecedented uncertainty Sunday when he announced he was ending his reelection campaign just weeks before his party's convention and endorsing Vice President Kamala Harris to be the party's next presidential nominee.

What comes next is anyone's guess.

Speculation over Biden's electoral future had been at a fever pitch since the president's presidential debate last month, but the party had not been able to come to a consensus on what would follow his departure from the election.

Ideas had included having Harris slide into the nomination given her spot on an existing national ticket and ability to inherit the funds from Biden's campaign. Others, however, have pushed for a mini-primary of sorts to test the rigors of would-be replacements, with many Democrats still thinking that Harris would be the frontrunner in such an impromptu contest.

Democrats are also still waiting to see who would jump into the race besides Harris, if anyone. Other names that had been bandied about include Kentucky Gov. Andy Beshear; North Carolina Gov. Roy Cooper; Maryland Gov. Wes Moore; California Gov. Gavin Newsom; Illinois Gov. JB Pritzker; Pennsylvania Gov. Josh Shapiro; Michigan Gov. Gretchen Whitmer; Georgia Sen. Raphael Warnock and more.

Some of those lawmakers have tweeted out praise for Biden, with Newsom dubbing him " one of the most impactful and selfless presidents" -- but none had thrown their hats into the ring as of early Sunday afternoon, and none had issued a quick Harris of endorsement.

Conversations will assuredly pick up around potential plans.

One plan, being circulated by Democratic National Committee Member James Zogby would create a condensed primary of sorts, with candidates having to secure the endorsements of 40 of 400 current DNC members, including four from each of the party's four regions. There would then be two televised debates, and the process would conclude when candidates would be formally nominated and voted on by delegates at Democrats' convention next month.

Such a process would surely be condensed -- Democrats' convention is at the end of August, leaving little time to sort through the rubble of Biden's departure before delegates formally pick a nominee. And delegates pledged to Biden would be free to pick whoever they want even though Harris was on Biden's tiocket, since the presidential and vice presidential ballots are separate at the Democratic convention. It's also unclear whether automatic delegates, formerly known as superdelegates, who aren't appropriated by primary results would not get to vote on the first round of nominating.

But some Democratic National Committee members believe the effort is worth it, and that the remaining calendar leaves enough time, if just barely.

"I hoped that it would have been done sooner, so that there would have been more time for the compressed primary that we had hoped for," Zogby told ABC News last week as chatter spiked that Biden would drop out. "But even with the time available now, it still can be done and should be done because it's better for the eventual nominee and the party that this not simply be a handoff, but that it be a process that is transparent and democratic."

Others, however, are urging the party to coalesce behind Harris.

As a Black woman, Democrats have said both that she could appeal to the party's most loyal demographic and that snubbing her would also serve as a snub to those voters. Polls have also shown that she performs better overall with Black and young voters than Biden, two key demographics with which Biden had seen his approval rating atrophy.

However, Republicans are champing at the bit to go after her over the administration's handling of the border, and her 2020 campaign was done in party by staff infighting, leaving it unclear the kind of campaign sprint she could run to November.

Still, having her take the reins could help limit chaos in an already muddled process, some Democrats have said. And she'll have powerful allies at her back.

South Carolina Rep. James Clyburn, a Democratic kingmaker, said as recently as Sunday morning that while he backed Biden, Harris would be the next up.

"Now that the donors and electeds have pushed out the only candidate who has ever beaten Trump, it’s time to end the political fantasy games and unite behind the only veteran of a national campaign — our outstanding @vp, @KamalaHarris!! Let’s get real and win in November!" Ron Klain, Biden's former chief of staff, posted on X Sunday.

No automatic delegate shift to Harris

Democratic delegates are "pledged" rather than "bound" to a candidate, and while party rules say that delegates "shall in all good conscience" reflect the views of those who elected them, there is no penalty if a delegate votes differently. This should make it easier for Democrats to adjust to this highly fraught situation.

These delegates would not automatically shift to Harris. The presidential and vice presidential ballots are separate at the Democratic convention.

Individual delegates now -- and suddenly -- have a lot of influence on whom their party nominates. There are about 4,700 delegates, both pledged and automatic(.

ABC News' Isabella Murray contributed to this report.