How voters will pick the Democratic presidential nominee is confusing. Some states hold primaries where voters have all day to vote, while others hold caucuses at a specific time where voters may have to wait around for more than an hour just to participate. In either system, the votes cast don’t directly elect a party’s presidential nominee. Instead, any candidate who wins at least 15 percent of the vote statewide or at the district level is allocated national convention delegates, and then those delegates choose the nominee. The ins and outs of this process routinely baffle voters, journalists and even presidential candidates.

And during the 2016 Democratic nomination contest, chaotic caucuses created even more complications. Controversy erupted right from the start when it was discovered that there was no mechanism for holding a recount in the Iowa caucuses, sparking an outcry from Bernie Sanders supporters who said the election was rigged to favor Hillary Clinton. Iowa and other Democratic caucus states also struggled to handle huge crowds of voters looking to make their voices heard. In reaction, the Democratic National Committee changed its rules in an effort to make nomination contests more inclusive, and many 2016 caucus states will hold primaries in the 2020 Democratic nomination contest — a change that could have ramifications for voter turnout as well as for which candidates have an edge in those states.

At least 10 states are planning to switch from a caucus to a primary in 2020. As things stand, just two states — Iowa and Nevada — have firm plans to caucus again. Two other 2016 caucus states — Maine and Wyoming — are still up in the air. Maine lawmakers may establish a government-run primary, in which case the Maine Democratic Party plans to move to a primary. And Wyoming Democrats are still ironing out some details. (The state party committee told FiveThirtyEight they plan to release an updated plan this summer.).

Democrats will hold fewer caucuses in 2020 Number of states planning to use each delegate allocation method for the Democratic presidential nomination contest (as of May 17, 2019) Method 2016 2020 Change Government-run primary 37 43 +6 Party-run primary 0 4 +4 Party caucus 14 2 -12 To be determined* — 2 2 Includes all 50 states and the District of Columbia. Territorial contests are not included. * Maine and Wyoming have not finalized the format of their 2020 nomination contests. Both are currently scheduled to be caucuses, but Maine may re-establish a government-run primary, which the state’s Democratic party will use if available. Wyoming Democrats are expected to announce further changes to their process later this year (Wyoming has no government-run presidential primary, but Democrats could hold a party-run primary). Source: Frontloading HQ, TheGreenPapers, State Delegate Plans

The 10 states switching to primaries fall into two groups: those with government-run primaries and those with party-run ones. In Colorado, Minnesota and Utah, Democrats are moving away from caucuses in favor of newly established state-run presidential primaries, and Democrats in Idaho, Nebraska and Washington have opted to use their states’ existing primaries rather than caucus again. But Democrats in four other states — Alaska, Hawaii, Kansas and North Dakota — will hold party-run primaries because those state governments don’t hold their own. This is an important distinction because government-run and party-run primaries can differ quite a bit. While state governments might open hundreds or thousands of polling places statewide for 12 hours or more, party-run votes might provide less than one voting location per county or keep the polls open for just four hours on primary day. These party-run affairs will likely offer forms of early and absentee voting in 2020, but seeing as they won’t be able to rely on the state-run systems that normally handle these kinds of election administration, it’s unclear how effective the parties will be at managing this on their own.

And some states, like Colorado and Minnesota, actually started shifting toward a primary system long before the DNC officially changed its rules in 2018. Elaine Kamarck, a senior fellow at the Brookings Institution who studies the nomination process, said that, in her view, “caucuses are kind of obsolete.” State parties often don’t have the resources needed to keep caucuses running smoothly and ensure everyone can access them, she said. “The participation in these hotly contested [presidential] primaries is so intense that caucus states have had a hard time handling them.”

But party reforms have also led to the increased use of primaries in 2020. Specifically, the DNC delegate-selection rules now say that state parties should try to use government-run primaries if they are available. And if a state party doesn’t have that option, party-run events (including caucuses) are required to allow absentee or early voting and same-day voter registration, plus implement procedures for recounts. For a state such as Washington, which was by far the largest caucus state by population in 2016, it was much easier to meet these rule changes by using Washington’s government-run primary than by adapting its caucuses.

One possible outcome of these changes is that we will likely see higher levels of voter participation because turnout tends to be higher in primaries than in caucuses. Caitlin Jewitt, a political scientist at Virginia Tech who has researched the effects of election rules on turnout in primaries and caucuses, told FiveThirtyEight that she believes moving to a primary system “could help turnout increase 17-18 percent.”

“The difference between having many hours [to vote] and having to show up on a Tuesday night [to caucus] is huge,” she said, and that increased flexibility helps draw in more voters.

The difference may be especially dramatic in the states switching from caucuses to government-run primaries, which offer lengthy voting hours. On the other hand, voter turnout may not change as much in the party-run primary states, where the party’s limited resources will affect how easy it is to cast a ballot. Still, state parties are also required to follow the DNC rules that encourage broader participation, so turnout could increase nonetheless. Josh Putnam, a lecturer at UNC-Wilmington and author of FrontloadingHQ, a blog following developments in the presidential nomination process, told FiveThirtyEight that he thinks “turnout in these contests will be higher than it would have been for traditional caucuses” but that “we will continue to see a gap between state-run and party-run contests in 2020.”

Of course, increased voter turnout could change which candidates benefit — or suffer — from that voting system. “The conventional wisdom is that caucuses favor more ideological candidates,” said Kamarck. Understandably, then, of the 2020 Democratic presidential field, Sanders is the candidate who’s often named as most likely to take a hit. In 2016, he won all 10 caucus states that are moving to some type of primary in 2020, though the field was far smaller in 2016, when most caucuses were head-to-head matchups between Sanders and Clinton. That said, Sanders probably owes some of his success in the caucuses to the fact that these low-turnout events tend to reward candidates who have strongly ideological and deeply committed supporters, and the move toward more primaries could erode that advantage.

“Caucuses benefit candidates who have strong grassroots campaigns but are also organized to get those grassroots supporters there,” said Jewitt. But since primaries are easier to participate in, candidates who have a bigger base (even if those voters are less engaged) may benefit from the format change. For example, in 2016, Nebraska and Washington held Democratic primaries in addition to their caucuses, though the caucuses determined delegate allocation and the primaries didn’t count. While Sanders handily won the caucus in each state, Clinton won the higher-turnout primaries.

However, not all experts were convinced that these rule changes would hurt Sanders or other “factional” candidates — those who draw passionate engagement but only from a small percentage of the party. As Putnam pointed out, Barack Obama was not a factional contender in 2008, but he won most caucus states. Like most nomination races, much will depend on how the candidate field winnows and how candidates adjust.

“Those with the resources will be the ones who are best able to adapt to the changes,” said Putnam.

Sanders currently holds a strong position in terms of resources, owing in part to his tremendous grassroots fundraising base. Moreover, with 20-plus Democrats running, Sanders’s small but intense base of support might be enough to put him ahead in a fragmented field. Putnam thinks Sanders’s chances depend “to a greater degree on there being at least three (or more) candidates in the race” than whether a state is holding a caucus or a primary.

So to recap, all we can say for sure about the move toward primaries over caucuses is that turnout will likely be higher in 2020 than in 2016 for the states that switch — and that could produce some interesting results.