Neither major party has required multiple votes to select a presidential nominee since the 1952 Democratic National Convention and the 1948 Republican National Convention. Yet, prolonged primary campaigns routinely fuel speculation that convention delegates might again be called on to choose a party's presidential nominee through multiple ballots, rather than to ratify a clear outcome from the primaries. This CRS Insight briefly addresses selected questions about possible contested Democratic and Republican conventions that might be relevant as Members of Congress prepare for the 2016 election.

What is a contested convention?

In general, a "contested convention" refers to delegates requiring more than one vote (ballot) to select the party's presidential nominee. Hence, contested conventions are also sometimes called "multi-ballot" or "open" conventions. Some contested conventions were "brokered" by party "bosses" before the two major parties (especially Democrats) changed their nominating processes beginning in the early 1960s.

Why is there speculation that a contested convention might occur in 2016?

This year, a Democratic candidate must secure at least 2,383 delegate votes to win the nomination. A Republican requires at least 1,237 votes. Because candidates from both major parties have remained competitive throughout the 2016 primary season, it is unclear whether one Democrat and one Republican will secure enough delegate support to be the presumptive nominee before the convention begins. Some Republican state parties allocate convention delegates proportionally, and Democrats require proportional allocation. Consequently, even candidates who do not win in a particular state can amass delegates throughout the primaries or other delegate-selection events.

Most speculation about a 2016 contested convention has emphasized the Republican race. On March 20, 2016, when asked about the prospects for a contested convention, Republican National Committee (RNC) Chairman Reince Priebus replied: "I think it's possible and we're preparing for that possibility." Those preparations reportedly continue. A contested Democratic convention appears less likely but some accounts suggest that one is possible, particularly if one candidate does not secure substantial "superdelegate" support in advance or if those delegates decided to change their intended votes or remain uncommitted.

What roles might Members of Congress play at contested conventions?

Although Members of Congress attend and participate in conventions, the events are not governmental or congressional functions. Regardless of whether a contested convention occurs:

How might convention rules affect a contest?

This Insight does not provide a comprehensive overview of all rules that might govern a contested convention, but the following could be especially relevant.

When will we know more?

If no candidate secures a majority of delegate votes before the end of the primary season, the odds of a contested convention increase, but candidates could campaign for delegate support until the conventions in mid-July. Most delegates will be allocated by June 7, when both parties hold primaries in California, Montana, New Jersey, New Mexico, and South Dakota. The nation's final primary occurs on June 14 in the District of Columbia (for Democrats).