But this time, the Republicans are not alone.
On Thursday, top Senate Democrat Harry Reid told CNN
he thought the prospect of his own party hosting a brokered or contested convention "would be kind of fun," saying "some of the old conventions produced some good people."
But DNC chairwoman Debbie Wasserman Schultz quickly sought to put a lid on the idea, telling
CNN's Jake Tapper that, like in 2008, the Democratic race would be "wrapped up in a timely process through the normal primary schedule."
Same for the RNC's Reince Priebus, who, despite reports in December that top Republican officials had deliberated over the potential of a messy post-primary nominating process, insists he is confident the GOP nominee will be in place soon enough.
"It's going to get old, it's going to get clarified, and it's going to feel like it was a long time ago when we're sitting in the middle of summer with a nominee," he told CNN's Wolf Blitzer on Wednesday.
But what if Priebus is wrong? What if no one clinches the nomination and the GOP descends on Cleveland in July with multiple candidates still vying for the party crown?
Here's a look at what would need to happen
over the coming months to create that wild scenario, and a few of the ways it could play out on the floors and backrooms of the Quicken Loans arena (which, we should note, does not
allow smoking anywhere on site.)
How do we get there?
The Republican party will assign 2,472 delegates through a state-by-state series of caucuses and primaries between February and June. To win the nomination, a given candidate requires a simple majority, or 1,237, of the total. The states holding their contests before March 15 are required by party rules to dole out their delegates proportionately, meaning 51% of the vote translates to the same percentage of the state's allotted delegates.
To further complicate the matter, there is the party's so-called "Rule 40."
This bylaw, added in 2012, states that any potential nominee must "demonstrate the support of a majority of the delegates from each of eight or more states." There are, as we approach the CNN debate in Las Vegas on Tuesday, a total of 14 candidates in the mix. No fewer than 10 can reasonably expect to win a noteworthy proportion of delegates as the race extends into spring.
For example, polls have shown Trump with a durable lead in Iowa -- he's up 13 points
on Ted Cruz, his closest rival, according to Monday's CNN/ORC poll -- but even then, his total support in this sprawling field is only 33%. Multiple candidates could win a majority in eight or more states, or no one could. Either way, it adds up to chaos on the convention floor. (Interestingly, the rule essentially prevents a would-be outside savior, like Mitt Romney, from parachuting into the process late, as that person would obviously arrive without those eight state majorities.)
One Republican with a full grasp of the RNC rules reached out after the story first published to point out that the eight-state requirement in Rule 40 is technically temporary. The RNC will vote on a new rule at the convention in 2016 and could again change the number of states at that time.
"Contested" or "Brokered" -- What's the difference?
Simply stated, if no candidate (and this goes for both parties) finishes the primary season with majority of delegates, the summer convention can be described as "contested." The last "contested" GOP primary came in 1976, when President Gerald Ford and an insurgent conservative named Ronald Reagan arrived at Kansas City's Kemper Arena short of a clinching total. Both campaigns sought to sway or romance their way to the necessary majority, which Ford would seal just before the first floor vote.
Because that initial ballot delivered Ford the nomination, the 1976 convention is not technically considered to have been "brokered."
For that, we have to look back more than 60 years, to the 1952 Democratic contest. Tennessee Senator Estes Kefauver led the race after the last round of primary voting, but did not win the nomination after the first floor ballot. No one did. It was not until the third ballot that Adlai Stevenson, the reluctant home-state governor with the backroom backing of outgoing President Harry Truman, finally emerged with the nomination.
When was the last one?
The most recent "brokered" convention for Republicans came four years earlier, in 1948, when they chose New York Gov. Thomas Dewey after three ballots.
Dewey, Stevenson and Ford all lost their general election contests.