GRINNELL, Iowa — When Democrats here went to bed on the night of their first-in-the-nation caucuses four years ago, the bitterly fought contest between Hillary Clinton and the insurgent Sen. Bernie Sanders was too close to call. So an abrupt predawn notice from the state party declaring Clinton the winner sent some into a fury.

Shaky videos of coin tosses deciding delegates in Clinton’s favor spread on Twitter. Stories multiplied of confused caucus-goers, untrained volunteers and mathematical inconsistencies, all amid a wave of suspicion that the party was manipulating the process for Clinton’s benefit.

“I never got a satisfactory explanation for how they arrived at their number,” said J. Pablo Silva, a historian at Grinnell College who wasn’t alerted when the state party transferred a delegate from Sanders to Clinton in the precinct in this small college town where he was serving as a caucus secretary.

Now, as Iowa Democrats hurtle once again toward the opening faceoff of a hard-fought presidential primary cycle — with at least four candidates seemingly in contention to win Iowa’s Feb. 3 contest — some in the party fear that reforms put in place to prevent the disarray of 2016 may create an entirely new set of problems in 2020.

It has long been the tradition here that voting plays out in school gyms and church basements, with multiple vote tabulations as supporters of candidates who do not reach a threshold on the initial vote scramble to make a second choice among the remaining contenders. This year, for the first time, the state party will release the initial raw vote totals as well as the final delegate allocation.

The change will mean more transparency, but it also will add to the workload of party officials and volunteer leaders — and it raises the possibility that multiple campaigns could claim a victory of sorts, with supporters of one candidate seeing another’s triumph as illegitimate.

The changes have yielded a thick new rule book for caucus organizers, who have undergone months of training on matters including new reporting requirements, mathematical formulas for delegate allocation, and combating false rumors that may spread online and cast doubt on the results. Some who have participated in the training sessions say the new system feels even more daunting than the old one.

Adding to the anxiety is the closeness of the race, which once again features an ascendant Sanders (I-Vt.), whose backers are on guard for any hint of irregularities, as well as the sense that any controversy over the results could hamper efforts to unify Democrats before the eventual nominee faces President Trump in November.

“We were cognizant about wanting to make it less confusing,” said Norm Sterzenbach, a longtime Democratic strategist in Iowa who was involved in planning for the caucuses until he signed on last year with former congressman Beto O’Rourke (D-Tex.), and then with Sen. Amy Klobuchar (D-Minn.). “But making the process more rigorous of course adds new complexity.”

In a way, the caucus process is insulated from cybersecurity threats and other concerns looming over more-traditional voting processes. There are no voting machines to hack. Instead, caucus-goers register their preferences in plain view of one another. In theory, any confusion could be ironed out through deliberation.

“In any election, even for school board or dogcatcher, there is rumor and innuendo,” said Matt Paul, who ran Clinton’s Iowa campaign in 2016. “The difference in Iowa is that it’s all in the open. You have to stand up in front of your friends and neighbors and tell them who you’re supporting and why.”

But the 2016 experience revealed how easily confusion and chaos can take hold.

In the Grinnell precinct where the delegate was transferred, uncertainty had reigned for much of the night. The Sanders supporters were “incredibly disorganized,” said Silva, and ended up having to count multiple times because the number they presented was implausible. Meanwhile, Iowans supporting Martin O’Malley, the former Maryland governor, grew frustrated and left. Andy McGuire, the state Democratic Party’s chairwoman at the time, said the overnight delegate transfer was necessary to correct an input error.

Across Iowa, however, the videos of coin tosses stoked outrage, even though the practice is routine — being used to allocate leftover delegates depending on the breakdown — and favored Sanders in certain cases, as well. As doubt took hold about the razor-thin margins, calls for a recount intensified. But Iowa Democratic leaders said that was impossible. “People physically aligned in groups,” the state party’s communications director said at the time. “There are no paper ballots to recount.”

Sanders called on the party to report a raw vote count. When the party leadership said it lacked the capacity to do so, Sanders’s supporters took to Reddit in a quest to uncover the numbers. On the Republican side, supporters of then-candidate Donald Trump suggested on social media that Microsoft, whose software was used to tally votes, had tilted the contest against their candidate. Trump himself claimed without evidence that Sen. Ted Cruz (R-Tex.), who narrowly won in Iowa, “illegally stole” the caucuses.

The Des Moines Register called the caucuses a “debacle,” singling out the Democrats for blame and finding, “Once again the world is laughing at Iowa.”

“The Iowa Democratic Party really learned from 2016,” said Steven Drahozal, the Democratic chairman in Dubuque County.

Part of the party’s learning involved realizing, from the special counsel’s investigation of Russian interference in the presidential campaign, how suspicion of the caucus process became a seed for the Kremlin’s influence campaign. In August 2016, Russian operatives using social media sowed doubt about the integrity of Iowa’s result, in an apparent effort to undermine Clinton’s legitimacy as she prepared to face Trump. An ad promoted by Russian actors on Facebook alleged that “Hillary Clinton has already committed voter fraud during the Democrat Iowa Caucus,” according to a federal indictment of multiple Russians filed in 2018.

For party officials here, the revelation underscored the need to arm staffers against not just cyberattacks but also against false narratives that are amplified on social media. Iowa Democrats say they are conscious of how quickly rumors about manipulation and backroom dealings can spread — particularly if amplified by Trump, who has shown keen interest in influencing the outcome of the Democratic primaries.

“Disinformation is something new we saw last election cycle, but people didn’t know it was happening at the time,” said Troy Price, the chairman of the Iowa Democratic Party. “Here, we know it’s going on, and we’ve had time to prepare for it.”

The state party, along with its Republican counterpart, partnered with the Defending Digital Democracy Project at Harvard’s Belfer Center for Science and International Affairs. The project’s leaders conducted a simulation with the parties in November. They were joined by security experts as well as developers behind the websites and mobile apps used by the parties to publicize caucus details and report returns.

Details of a mishap would arrive via email, bringing news, for example, of an app malfunction or of specious tweets claiming that the caucuses actually would begin at 8 p.m., an hour later than the official 7 p.m. start time. A space was cordoned off for mock news conferences, where people pretending to be reporters clamored for updates.

Democrats used the simulation to develop possible plans for caucus night — including contingencies such as bringing in the Department of Homeland Security and contacting executives at Twitter.

Some of the more complex changes arising from the breakdown in 2016 involve the handling of results on caucus night.

The voting involves Iowans’ assembling in groups to signal their support for one candidate or another. These groups are known in caucus parlance as “alignments.” The relative sizes of the alignments are used to calculate delegate allocations. In most precincts, delegates are allocated only to candidates who receive at least 15 percent of the vote.

A candidate wins the caucuses by securing the most projected delegates to the state convention, which translates in turn to delegates to the party’s national nominating convention. This year, the party will release raw totals from the first as well as the second alignments — as different factions jostle for support and seek to win over undecided caucusgoers. The totals will be recorded by tallying “Presidential Preference Cards,” which will also provide a paper trail should a problem arise with the mobile app used to report returns.

In another change from past cycles, only members of alignments that are not large enough to reach the 15 percent threshold will be allowed to shift to other groups, a procedure known as realignment. For groups above the threshold, the count will be locked in, and those caucus-goers will be able to go home. Further, national delegates will be allocated once caucus-night results come in, rather than over the course of county and district conventions.

The delegate selection plan spells out a process for candidates to request a review of caucus results, as well as a timeline for the state party to respond.

And, in yet another change, the state party approved nearly 100 satellite caucus locations, where Democrats who completed preregistration by Jan. 17 will be able to participate. The sites include three places abroad where expatriate Iowans took the initiative to apply to host caucus assemblies — Glasgow, Scotland; Paris; and Tbilisi, the capital of the former Soviet republic of Georgia. A 10-person review committee weighed applications on the basis of each location’s accessibility, proximity to other precincts and demonstrated need for the site.

A plan to allow Iowans to participate by phone in a virtual caucus was scrapped last year when national party leaders said there wasn’t technology that could be protected from hacking. The decision highlighted the premium placed on security, which won out over the desire for greater accessibility.

Still, the reforms amount to the “most significant changes to the Iowa Caucuses since 1972,” the party says on its website.

The changes are also proving to be confusing, even to some old Iowa hands. Lyz Lenz, a columnist for the Cedar Rapids Gazette, recently completed the online training prepared for caucus chairs and came away bewildered, confused especially by the calculation required to apportion delegates. “I can’t say exactly, but I know you have to divide something by six,” she said.

At town halls, candidates are fielding questions about the rules and “strategy” for securing delegates on caucus night.

Responding to one such query recently, the entrepreneur Andrew Yang said that “we have done the math, and here in Davenport, we believe we’ll be well over the 15 percent threshold.”

A record turnout, which is expected, could deepen the confusion, said McGuire, the former party chair who is running Klobuchar’s Iowa campaign.

County chairs and other Democratic officials are in overdrive trying to prepare the volunteers who preside on caucus night. In a recent email to Democrats in Dubuque County, Drahozal urged caucus leaders to complete the training and take an accompanying test.

Rules and procedure aside, Drahozal said, party leaders can take steps to protect the integrity of the process. He is remaining “adamantly, adamantly neutral” until caucus night.

That sort of forbearance is a sign of the times, said Sterzenbach, whose extensive knowledge of Iowa’s singular political tradition has earned him the nickname “Mr. Caucus.”

The contest in “2016 was so close, and it showed how much distrust of the system there was,” he said. “Much work went into addressing that.”