LAS VEGAS - With the Nevada caucuses days away, campaign officials and Democratic activists are increasingly alarmed that they might prove a debacle as damaging as the vote in Iowa, further setting the party back in its urgent effort to coalesce around a nominee to take on President Donald Trump.

Campaigns said they still have not gotten the party to offer even a basic explanation of how key parts of the process will work. Volunteers are reporting problems with the technology that's been deployed at the last minute to make the vote count smoother. And experts are raising serious questions about an app the party has been feverishly assembling to replace the one scrapped after the meltdown in Iowa.

"It feels like the [state party is] making it up as they go along," said one Democratic presidential aide, who spoke on the condition of anonymity to discuss the process. "That's not how we need to be running an election."

Adding to the challenge is the complexity of Nevada's caucuses. Unlike in Iowa, where caucuses are conducted in one evening, Nevadans have the option of voting early. At sites across the state, Democrats can rank their top presidential choices on a paper ballot.

On Saturday, caucus day, Democrats can gather at one of about 2,000 sites to vote for their preferred candidate. If their first choice doesn't get enough backing, voters can throw their support behind someone else, a second round of voting known as "final alignment." Early voting preferences will be treated the same way, as though the voter were attending in person.

The party had planned to use two specially designed apps for reporting results, developed by political technology firm Shadow, the same company that designed the vote-recording app blamed for the chaos in Iowa. A coding error in the Iowa app made it impossible to tally results, prompting confusion and delays. Shortly afterward, Nevada Democrats announced that they were scrapping the Shadow products.

Since then, state party officials have issued a series of memos trying to explain how things will work. But the party has left crucial questions unanswered, 2020 campaign aides say.

"If the party had this process well-defined and had confidence in it, I think that we'd know a lot more about it," one of the Democratic aides said.

State party officials have strenuously denied a lack of communication, pointing to group conference calls and briefings they've held with 2020 officials as they quickly retooled their caucus process.

"We are in constant contact with the campaigns," said a state Democratic Party official, who spoke on the condition of anonymity to speak more candidly about the process. "We communicate at a very high level with the campaigns . . . and we have kept them informed every step of the way."

But several campaigns complained that those interactions seemed designed to avoid questions. On Monday, aides from different campaigns said they were given just minutes notice for an evening conference call announcing a key decision about early voting. The call was so sudden that one top campaign aide, in the middle of a caucus training for volunteers, was unable to join.

On Thursday, when the party released an update on early voting, several campaigns said they learned of the memo from reporters before they received it from the party. "We have been learning more about this process from the media than the state party or the DNC," said a Democratic aide, who also spoke on the condition of anonymity.

Meanwhile, several campaigns complained that the conference calls they had held with party officials had only increased their sense of alarm that something could go wrong.

One 2020 aide, speaking on the condition of anonymity so as not to sour relations between the aide's campaign and the state party, likened the calls to phoning into a "call center where the customer service person only had three prompts that they use." The Nevada Democrats' staff, joined on the call by their attorney, offered vague answers that seemed to have been scripted by a legal team to offer as little substance as possible, the aide said.

Aides for several campaigns said this left them in a tough position, torn between trying to be publicly optimistic about a potentially flawed caucus vote in a politically important state and raising concerns.

"All of us, every campaign, regardless of policy position or strength in the race, we all want that process to work. And there's a disincentive to . . . screaming from the rooftops about how this all might not work," said a Democratic aide, who also spoke on the condition of anonymity so as not to anger Nevada Democrats.

Several campaigns said they contacted the Democratic National Committee with their concerns. All said they had received no response back - with one campaign likening the DNC to a "brick wall."

"They are the ones who also can demand answers," one of the Democratic aides said. "They are supposed to be the ones who are the adults in the room who can trust and verify. And that hasn't happened, to our knowledge."

A DNC official pushed back on that claim. "The Nevada State Democratic Party and the DNC are in regular communication with campaigns and will continue to answer questions about the process in the state and the nominating process," DNC spokeswoman Xochitl Hinojosa said in a statement. "We are confident that they are doing everything they can to implement lessons learned in Iowa, and we have deployed staff to help across the board, including tech support and volunteer recruitment."

A state party official also said the party had invited campaigns to observe early caucusing and plans to allow representatives to observe the ballot processing as the party prepares the data for Saturday's in-person voting.

Experts also have raised serious concerns about the state party's plan for tallying votes on caucus night.

Nevada officials have said they plan to use a Google-based form, pre-installed on party-purchased iPads, to register voters when they arrive during early voting. Those voters will then be given a paper ballot to rank their candidate choices.

Those ballots would be verified and scanned at processing centers before they are somehow transmitted to precincts for the in-person caucuses. On caucus night, caucus administrators will access the early vote data through a Google Forms-based web application the party has referred to as a "Caucus Calculator" on party-issued iPads.

Some technical aspects of how the iPad software will work are unclear. According to the party, the iPads will be connected to the Internet using cellular and WiFi connections. Party volunteers, who have been training to run the caucuses, have been told that the Google Form will work, even if an Internet connection is not available.

But Google Forms does not offer offline support, raising more questions.

"Browser-based forms don't work well," said Joe Verschueren, founder of Formutus, a company that makes customized forms that can interact with Google Forms. Verschueren said that to make its software work offline, the Nevada Democrats will have to have a mobile app downloaded directly onto the iPad.

The party has not said whether that is the case.

The other problem, Verschueren said, is that Google Forms is limited in how it can be customized, which could present challenges for the party if it is trying to make the software perform the complicated work of folding the early vote tallies into the caucus night results. "Google Forms is very simple," he said.

Nevada Democrats said their new process reflected input from independent security experts, the DNC, the Department of Homeland Security and Google, which was consulted "to ensure the process would remain secure."

"We understand just how important it is that we get this right and protect the integrity of Nevadans' votes," Nevada State Democratic Party Executive Director Alana Mounce wrote Thursday in a memo to presidential campaigns. "We are confident in our backup plans and redundancies."

But it's not clear exactly how the party has been working to vet security issues. DHS did not respond to a request for comment on its involvement.

Volunteers also have begun sounding the alarm, saying party officials have left them unprepared. Seth Morrison, a volunteer site leader, had publicly raised concerns about the party's mixed messages to volunteers and the lack of hands-on training on the Caucus Calculator.

He said several people have raised questions about different scenarios they might encounter, such as whether an early vote with no viable candidates should be thrown out. Nobody seems to know, he said.

The first day of early voting did little to ease worries. On Saturday, there were long lines all over the state for early caucusing. More than 18,538 people turned out, according to the state Democratic Party.

Volunteers in some precincts reported technical issues, including problems with the Google Form-based registration that led some sites to switch to paper. State party officials blamed those issues on high turnout, not technical problems.

That day, state and party officials spread out across the state, appearing at early voting sites to insist Nevada's process would be a lot smoother than Iowa's.

"The [early vote] is going to make Nevada look good," former Senate majority leader Harry Reid said outside a voting site at a public library in East Las Vegas, calling out the "debacle that happened in Iowa."

Outside an early vote site in Las Vegas's Chinatown, Rep. Dina Titus, a Democrat who has endorsed former vice president Joe Biden in the race, said she was concerned but optimistic.

"We've learned from Iowa. We're not using that same app," Titus said. "We don't want anybody to kind of question the legitimacy of the result. So, we've had a little more time."

"Might have been nicer to have a little bit more time," she added.

The Washington Post’s Reed Albergotti, David Weigel and Elise Viebeck contributed to this report.