Both national parties, but especially the Democrats, are prone to tinkering with the mechanics of the presidential nomination process in the period between elections, in a constant scramble to respond to various problems and complaints that reliably emerge during every competitive nomination contest. The Democratic National Committee's most urgent priority after the 2016 election was to remedy the perceived legitimacy crisis within the party that arose from the presence of unpledged superdelegates, which had caused a fair amount of public controversy during the Clinton-Sanders race that year. After considering a range of proposed reform measures, the DNC ultimately decided to keep superdelegates but deprive them of the power to cast decisive votes on the first presidential nomination ballot at the national convention.
But the party also approved another change to nomination procedures that has received much less attention so far. For the first time, the DNC passed an official resolution encouraging the use of presidential primaries rather than caucuses to select pledged delegates, and required states continuing to hold caucuses to allow a means by which voters could cast absentee ballots or otherwise participate remotely. With relatively little attention, this reform seems to have immediately produced a notable effect on the 2020 nomination process.
The case against caucuses contains several distinct arguments. Critics are fond of pointing out that the participation level in caucuses is much lower than that of primaries. Even the well-publicized Iowa caucus produced a turnout rate of just 16 percent in 2016, compared to a 52 percent rate in the New Hampshire primary the following week. In other, less-hyped states, the caucus turnout rate fell into single digits—8.1 percent in Minnesota, 5.5 percent in Kansas, 4.6 percent in Hawaii. Caucuses are also especially difficult for specific subpopulations to attend: service-industry workers; parents of young children; people with disabilities or limited transportation options. (Concerns about such inherent biases in the caucus system is what ostensibly motivated the DNC to mandate the availability of absentee ballots in future state caucuses.)
Notwithstanding the comparatively depressed participation rates, unexpected surges in turnout have sometimes strained the organizational capacity of the state parties that manage the caucuses, producing full parking lots, long lines, and procedural confusion once inside. Some Mainers waited for over four hours to participate in their state's 2016 caucus, while some Minnesotans had to vote using Post-It notes in 2008 because their caucus sites ran out of ballots.
A final strike against caucuses, at least from the perspective of traditional party leaders, is their tendency to benefit insurgent candidacies with high supporter enthusiasm over the party regulars favored by more casual primary voters. In 2016, for example, Hillary Clinton defeated Bernie Sanders in the first two caucuses of the year by narrow margins (0.2 percent in Iowa and 5.3 percent in Nevada), but Sanders proceeded to sweep the remaining 12 state caucuses on the calendar, losing only the 4 caucuses held in U.S. territories that lack representation in the electoral college.
Presidential primaries are already the norm in the most populated parts of the country. In 2016, Democrats employed caucuses in 3 mid-size states (Colorado, Minnesota, and Washington); 11 small states (Alaska, Hawaii, Idaho, Iowa, Kansas, Maine, Nebraska, Nevada, North Dakota, Utah, and Wyoming); and 4 territories (American Samoa, Guam, Northern Marianas, and the Virgin Islands). A total of 561 delegates were selected in caucuses, representing 14 percent of all Democratic pledged delegates.
But as the 2020 nomination process comes into focus, it's clear that there will be notable movement away from the use of caucuses. According to political scientist Josh Putnam's invaluable FHQ website, which closely tracks such changes, all three of the most populous states that held caucuses in 2016 plus three more small states (Idaho, Nebraska, and Utah) have opted for government-run primary elections in 2020, with a seventh state (Maine) still considering whether to join them. The number of Democratic pledged delegates selected outside of state-operated primaries seems certain to decrease to less than half of its 2016 level, perhaps dropping to just 5 or 6 percent of all pledged delegates nationwide.
On top of that, a few of the remaining states that are not shifting to standard primary elections are still abandoning traditional caucuses in favor of a "firehouse" primary administered by the state party. According to Putnam, the state parties in Kansas, North Dakota, Alaska, and Hawaii are all planning such a change. These elections may wind up behaving like a cross between a primary and a caucus, with fewer balloting sites and shorter voting hours than a regular primary would have. But there seems to be a clear response at the state level to the DNC's post-2016 policy shift, with the pure caucus model of delegate selection suddenly falling out of favor in multiple places at once.
Does this mean that state caucuses are poised to be virtually irrelevant to future presidential nominations? From a purely mathematical perspective, it certainly becomes even less likely that the shrinking share of delegates chosen in caucuses turns out to represent the margin between national victory and defeat for a prospective nominee. On balance, that's mildly good news for "establishment"-style candidates (like, say, Joe Biden) and mildly bad news for "outsider" types (like, say, Bernie Sanders).
But the first and third states on the nomination calendar will persist in selecting delegates via traditional caucuses, and these states' temporal primacy gives them substantial influence over the outcome that is far out of proportion to the modest size of their convention delegations. As Putnam notes, both Iowa and Nevada have good reason not to abandon their caucuses for primaries, or even to lean too far in the direction of a caucus-primary hybrid: if they do, their jealous sibling New Hampshire would undoubtedly respond by claiming the right to push even further to the front of the line in order to defend its self-proclaimed perpetual right to hold the first primary in the nation. Unless the national parties act to disallow caucuses altogether, then, the distinctive demands that they place on candidates and voters will remain a key component of the highly complex and thoroughly unique manner in which American presidential nominees are chosen.