Sanders' campaign quickly followed suit, releasing its own unverified internal caucus numbers that portrayed the Vermont senator with a sizable lead in the Iowa delegate race.

"We recognize that this does not replace the full data from the Iowa Democratic Party, but we believe firmly that our supporters worked too hard for too long to have the results of that work delayed," Jeff Weaver, a Sanders senior adviser, said in a statement.

The outcome is a nightmare scenario that some campaigns had warned about in the lead-up to Iowa — an unclear result that allows multiple candidates to claim success and shreds the possibility of the 2020 race quickly gaining clarity.

Even if the Iowa Democratic Party is able to verify the results later on Tuesday, there is a risk that a cloud of uncertainty will hang over the eventual results.

With so much still unknown on Monday night and early Tuesday morning, the candidates scrambled to regroup, with Amy Klobuchar hitting the airwaves first with an address to supporters that did not seek to seize the top spot.

"You probably heard we don't know the results. But I did not want to let another minute go by without thanking all of you," Klobuchar said at her campaign headquarters. "We know there's delays, but we know one thing: We are punching above our weight."

The brief address served as a vehicle for Klobuchar to forge ahead to the second nominating contest, the New Hampshire primary next Tuesday, without having to confront a potentially disappointing outcome for her campaign.

She had staked much of her candidacy on an impressive outing in Iowa, and although zero percent of precincts had reported delegate totals by the time of her speech, initial entrance polls showed a close competition among four other candidates: Joe Biden, Buttigieg, Sanders and Elizabeth Warren.

By the end of the evening, however, Klobuchar's campaign manager asserted online that she had possibly outperformed Biden in the caucuses.

"Big night in Iowa," tweeted Justin Buoen. "With the numbers we’ve seen internally and publicly, we’re running even or ahead of Vice President Biden. Wheels up to New Hampshire!"

Biden also appeared to acknowledge his longshot chance of victory in the state, even as he offered a position spin, saying he was "feeling good" about the caucus results.

"The Iowa Democratic Party is working to get this result — get them straight. And I want to make sure they're very careful in their deliberations," Biden said in his speech to supporters. "And indications are — from our indication it's going to be close. We're going to walk out of here with our share of delegates. We don't know exactly what it is yet, but we feel good about where we are."

Sanders, who entered caucus day as the prohibitive frontrunner, struck an optimistic tone in his own speech before his campaign released the internal numbers, remarking that "when those results are announced, I have a good feeling we're going to be doing very, very well here in Iowa."

Characterizing the Iowa contest as "too close to call," Warren was similarly optimistic but did not predict a win for herself. "We don't know all the results tonight, but tonight has already showed that Americans have a deep hunger for big structural change to make our economy and our democracy work for everyone," she said.

Warren campaign chief strategist Joe Rospars, meanwhile, took sharp jabs at Buttigieg and Sanders on Twitter, writing that "Any campaign saying they won or putting out incomplete numbers is contributing to the chaos and misinformation."

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But Rospars ranked the top-tier candidates' showings in the state, describing the state of play as a "very close race among the top three candidates (Warren, Sanders, Buttigieg)," adding that "Biden came a distant fourth."

Greg Schultz, Biden's campaign manager, appeared to knock those posts by Warren's aide, and tweeted that the campaign was "thrilled" with the former vice president's performance. "We believe we will emerge with the delegates we need to continue on our path to make Joe Biden the Democratic nominee," he wrote.

Andrew Yang also weighed in on the debacle by the Iowa Democratic Party. He told supporters at a Des Moines event that he was headed "right from here to New Hampshire," and tweeted: "It might be helpful to have a President and government that understand technology so this sort of thing doesn’t happen."

Tom Steyer did not explicitly weigh in online, instead tweeting earlier in the evening that he and his campaign were "carrying our message on to NH, NV, SC, and beyond."

James Arkin and Nolan McCaskill contributed to this report.