A “contested convention,” sometimes also referred to as a “brokered convention,” occurs when no single candidate for president secures the majority of delegates needed to win a political party’s nomination in advance of that party’s convention.
When that happens, a candidate might still get enough delegates by the time that the convention’s first ballot starts, but if that fails to occur, then the delegates become free to vote for whichever candidate they want, leading to a situation in which the convention becomes ‘contested’ or ‘brokered.’
In a contested convention, depending on the rules of the party, all regular delegates who were pledged to support a certain candidate during the primary voting process are “released” and can be convinced to support someone else.
For most people who follow politics, a contested convention conjures up images of “multiple ballots, horse-trading, smoke-filled rooms, favorite sons, dark horses and other colorful elements that have enlivened American political journalism…,” as described by Pew Research.
Parties try to avoid contested conventions because they typically signal that a party is fractured, split and not unified going into a presidential election.
But that doesn’t stop the speculation that precedes almost every convention. From the Washington Post: “Speculation about a brokered, deadlocked or contested political convention surfaces every four years with the regularity of Brigadoon rising from the mist…. Such predictions show up in virtually every cycle when there’s even a hint of the possibility — usually early on, when a platoon of still-viable candidates suggests that a divided primary contest will fail to produce a winner.”
But as frequently as they’re predicted, contested conventions have almost never come to pass in the modern electoral system.
From The Week: “Since the GOP’s first convention in 1856, there have been 10 presidential elections in which no Republican candidate came into the convention with a majority of delegates. In seven of those elections, the eventual nominee was not the person who had the most delegates at the start of the convention. Of those 10 brokered conventions, six of them produced a Republican nominee who went on to win the general election Since 1952, no convention — Republican or Democratic — has gone beyond the first ballot.”
That year, in a hot and stuffy Chicago, Adlai Stevenson blew the Democratic convention wide open, and was eventually nominated for president on the third ballot.
In 1984, there was a close call when Democrat Walter Mondale arrived at the Democratic convention 40 delegates short of outright victory. But when the superdelegates supported him, it pushed him over the top to the nomination.
The modern primary system still awaits its first truly contested convention.