It's a dream of political junkies and campaign reporters that hasn't happened since 1952 — a contested political convention. And it could happen this summer.

That's because the delegate slog ahead for 2020 Democrats gives them little incentive to drop out, since any one of the six could still have a shot at nabbing the party's nomination at its national convention, set for July 13-16 in Milwaukee, Wisconsin.

Contests in Iowa and New Hampshire dramatically reshaped the historically crowded primary field and left a half-dozen candidates with an arguable pathway to the nomination.

They knocked former Vice President Joe Biden down from front-runner status and showed Vermont Sen. Bernie Sanders to be a leader in the popular vote. Former South Bend, Indiana, Mayor Pete Buttigieg proved viability as a candidate by doing well in both contests and leads in Democratic National Convention nominating delegates.

Minnesota Sen. Amy Klobuchar got a boost from better-than-expected placings in both states, and Massachusetts Sen. Elizabeth Warren still sees a path to the nomination. Meanwhile, former New York Mayor Michael Bloomberg is waiting in the wings for March 3 Super Tuesday states with a bottomless source of campaign funds.

FiveThirtyEight’s primary forecast model, which attempts to use polls to predict delegate allocation in the primary cycle, finds that the two likeliest outcomes are a contested convention and Sanders winning the nomination, each with roughly 2-to-5 odds.

A candidate needs a majority of pledged delegates, at least 1,991 of the 3,979 available, allocated based on results in state primaries and conventions, in order to win the presidential nomination on the first ballot at the July convention.

If no candidate wins a majority, around 770 automatic “superdelegates” made up of party leaders, such as DNC members and Democratic members of Congress, are permitted to vote for whomever they wish on the second ballot, creating the possibility that a candidate who did not win the most pledged delegates wins the nomination.

In previous years, superdelegates voted on the first ballot. But the rule was changed in an attempt to make a fairer process after complaints from far-left Sanders supporters in the fallout from the 2016 primary cycle.

“Brokered conventions are the stuff of political scientists' dreams, not political reality. However, by removing superdelegates from the first balloting, the DNC made it much more likely this cycle than any since 1972,” said Democratic strategist Kenneth Baer, a speechwriter for the 2000 Al Gore campaign and adviser to the 2004 Joe Lieberman and John Kerry campaigns.

A Feb. 17 internal Bloomberg campaign memo warned that if his more moderate competitors in field — Biden, Klobuchar, and Buttigieg — do not drop out of the race, their ideological nemesis Sanders is poised to amass a delegate lead starting with March 3 Super Tuesday contests.

But the possibility of being able to win the nomination based on superdelegates in a contested convention tempts candidates to stay in the race if they see progress in some areas.

“As long as it's a wide-open race with no clear front-runner, there’s some incentive to stay in, especially if you still got some resources coming in,” said Democratic strategist Mike Lux, who worked on Bill Clinton’s 1992 campaign and Barack Obama’s 2008 transition team. “It's entirely possible that folks could stay and just gather as many delegates as they can.”

No convention on either side of the aisle has gone more than one round of balloting since the 1952 Democratic gathering in Chicago, when Illinois Gov. Adlai Stevenson won on the third round. But the fractured nature of this year's early contests suggests even 2020 Democratic candidates with seemingly little chance of winning can still hold out hope.

Elizabeth Warren's campaign is already making her pitch for staying in the race despite lackluster placing in the Iowa caucuses and New Hampshire primary. Last week, Warren's campaign asserted that only she, Sanders, and Biden have delegate-worthy levels of support in upcoming contests.

The five top-polling candidates (Sanders, Biden, Bloomberg, Warren, and Buttigieg) are all in double-digits in RealClearPolitics’s average of primary polls, the first time five candidates have polled above 10% in this primary cycle.

“As long as other candidates have money to compete, they have an incentive to gather as many delegates as possible,” Baer said.

Even if Sanders tumbles in the polls or future primary contests, he could still gobble up delegates and prevent others from getting a majority.

“When you have a candidate, like Sanders, who is not even a member of the party he seeks to lead, he is motivated more by his cause than what is best for the party. Thus, Sanders has almost no incentive to drop out before Milwaukee, no matter the results,” Baer said.

No major party convention has gone to multiple ballots in the modern political era, and a messy, public nominating fight has the potential to dampen Democratic enthusiasm in the general election. But in two recent times parties had messy convention fights, their nominee lost in the general election.

In 1980, Democratic Massachusetts Sen. Edward Kennedy sought a rule change that would allow delegates to vote as they wished on the first ballot in a challenge to President Jimmy Carter. In 1976, Ronald Reagan’s team proposed a rule change that would force eventual Republican nominee Gerald Ford, the incumbent president, to announce his running mate before the first delegate vote.

Lux noted, however, that President John F. Kennedy won the 1960 election despite a tense last-minute scramble to secure delegates, and suggested that a convention fight might not hurt the party this year.

“In some ways having people sitting around a table and talk to each other, cut some deals, might be a healthy thing,” he said.

In Wednesday’s Democratic presidential debate, each candidate was asked if they think a candidate who wins a plurality of pledged delegates, but not a majority, should be the nominee. All of them except Sanders declined to support the idea, signaling a hope that they could win on the second ballot with superdelegates.

With a possible convention fight on the horizon, Democratic presidential hopefuls must court support from superdelegates and carefully plan campaign stops. While some pledged delegates are allocated based on statewide votes, others are allocated based on votes within congressional districts.

“Focus in on several key congressional districts where you think you can be strongest, and you try to win as many delegates there,” Lux said.

“Smart campaigns would be wise to retain or hire a DNC rules expert,” Baer said.