HENDERSON, Nev. — It took four hours on Saturday afternoon to count just 4 percent of the results from the Nevada caucuses.
That didn’t stop The Associated Press from calling the state for Senator Bernie Sanders, but it did cause a lot of confusion — and continued to do so late into the night — about why counting caucus results takes so long.
Officials with the Nevada Democratic Party and the Democratic National Committee stressed all week that they had gone to school on lessons learned from the bungled Iowa caucuses, when a smartphone app for reporting results crashed and phone lines to report results were jammed for hours.
But by 10:30 p.m. Eastern time — more than seven hours after Nevada’s caucuses began, and four hours after most of them closed — Nevada Democrats still have only reported results from about 23 percent of the state’s precincts.
The tardiness stems from new caucus rules mandated by the D.N.C. that require the state party to collect more than 100 data points from each of Nevada’s 2,097 precincts. The state party also installed a duplicative reporting system to try to prevent Iowa-style mishaps that led to a litany of mathematical errors that had to be corrected later.
Nevada’s protracted vote-counting served to rob several Democratic candidates who had hoped to claim a second-place finish on Saturday night and position themselves as the moderate alternative to Senator Bernie Sanders, who won what appears to be a commanding victory in Nevada.
The dearth of results didn’t stop both former Vice President Joseph R. Biden Jr. and former Mayor Pete Buttigieg of South Bend, Ind., from declaring that their internal figures showed them finishing in the next slot after Mr. Sanders. Nevermind that even under their sunny projections, each would be some 20 percentage points behind the Nevada winner.
The vote-counting was slow, in part, because for nearly two hours after most caucuses were completed, the state party’s results hotline was so jammed that callers found themselves getting busy signals or messages that their calls could not be completed as dialed.
A little after four hours after the caucuses began, volunteers received a text from the state party with three new phone numbers to call to report results. Caucus precinct chairs found these numbers had operators who answered the phones and could take their results.
After Iowa’s caucus reporting system crashed with about 80 phone operators in Des Moines earlier this month, Nevada had 200 operators on site at the Rio Convention Center in Las Vegas. When reports came in about phone lines being jammed, the party texted its volunteers with the three new phone numbers — a move precinct leaders said made it far easier to reach an operator to report results.
“They did gave three different numbers and said if we couldn’t get through they would call us back,” said Ruben Murillo, a precinct chair at Coronado High School in Henderson.
Phil Sobutka, who spent more than 30 minutes dialing and redialing the party’s results hotline after his Henderson caucus finished, said the new number worked the first time he tried it.
Still, the process of reporting caucus results under the current D.N.C. rules is a long one.
Nevada’s caucus had 12 names on its ballot — 11 candidates and uncommitted. (Several candidates who have dropped out of the race remained on the ballot.)
For each candidate, Nevada precinct leaders had to report six sets of results — early votes, in-person votes and total votes for both the first alignment and second alignment. Then the precinct leaders had to report delegate totals for each viable candidate, as well the viability threshold for the precinct.
The phone operator would confirm each number with the precinct volunteer. And then once the data had been collected by phone, it would be checked against a photograph of worksheet the precinct volunteers were instructed to text to party headquarters.
In an echo of Iowa’s slow reporting process, Nevada volunteers estimated it took them between 10 and 15 minutes to read through all the results with the phone operators at party headquarters.
In its past caucuses, Nevada reported results much faster in part because it had to report only one set of numbers from each precinct: how many delegates each viable candidate won. This was typically three, or maybe four numbers, depending on how many viable candidates there were.
But allies of Mr. Sanders, who still believe they would have won Iowa and other caucus states in 2016 had the system been more transparent, forced the D.N.C. to adopt new rules requiring 2020 caucus states to report not just the number of delegates each candidate won — the traditional metric of measuring caucus success — but also the number of supporters each candidate had on the first and second alignment.
Several unknowns remained late Saturday night, not least the timing of the full results and the breakdown in delegates won by each candidate. But probably the biggest unknown: Whether the Nevada result tabulations would end up rife with errors and inconsistencies like the Iowa results were.