Two Contested Conventions? It Wouldn't Be The First Time

— -- New speculation about the possibility of Democrats having a contested convention -- in addition to the already likely scenario that Republicans will have one –- could add 2016 to a small list of historic presidential races.

The prospect of having dual contested conventions is far from set, but if it were to happen, it wouldn't be the first time.

Historical Precedent

Four other elections included contested conventions where both Democrats and Republicans determined their nominee past the first ballot, according to a review of post-Civil War elections by the Pew Research Center.

Three of those elections were consecutive: 1876, 1880, and 1884. The fourth was in 1920.

Pew analyzed elections after the Civil War and up through 1984, since that was the last time a party's nominee was uncertain going into the convention. Including elections since 1984, there have only been 18 contested conventions with more than one ballot, out of 74 total conventions.

That means three quarters of all conventions since the Civil War have been decided either before the convention convened or during the first ballot vote.

Some Record-Breaking Battles

The last candidate who won the nomination after multiple ballots and then went on to win the general election was Franklin D. Roosevelt in 1932. He won the Democratic nomination after four ballots.

But, four ballots wasn't the highest number of rounds that a winning nominee required. Woodrow Wilson holds the title of having the highest number of ballots -- 46 -- for a nominee who went on to win the general election.

When it comes to the general election losers, that title goes to John Davis, a former Ambassador. In 1924 he beat the two favored Democratic nominees -- William McAdoo and New York Gov. Al Smith -- to win the party's nomination on the 103rd ballot. He lost the general election to Herbert Hoover.

What's Next for 2016

The Republicans have a fairly likely possibility of having a contested convention, according to the delegate math.

On the Republican side, ABC News analysis puts Donald Trump's total delegate count at 743 with Sen. Ted Cruz in second with 517 delegates. Gov. John Kasich, the only other Republican running, has 143 delegates -- less than Sen. Marco Rubio who dropped out of the race with 171 pledged delegates.

The magic number a Republican candidate needs to obtain to become eligible for the nomination is 1,237.

Trump would need to win 60 percent of all remaining delegates in order to reach 1,237 before the convention, while Cruz would need 87 percent and Kasich would need the mathematically impossible 132 percent.

For Democrats, a contested convention is less of a possibility

Speculation over the prospect of a Democratic contested convention comes mostly from Jeff Weaver, Sen. Bernie Sanders' campaign manager. Weaver claims that neither Sanders nor Clinton will amass a majority of pledged delegates before the July convention.

The center of his argument is the differences between pledged and bound delegates. Clinton has a far greater number of pledged delegates in her corner, but they are technically allowed to change their support at any point until the convention vote.

Right now, ABC News analysis has Clinton leading with a total of 1,749 delegates and Sanders with a total of 1,061 delegates. That gap drops dramatically when the superdelegates are taken out: Clinton has 1,280 pledged delegates and Sanders has 1,030 pledged delegates. A Democratic candidate needs 2,383 total delegates to be eligible for the nomination.

“The way the math is right now, it is very, very, very unlikely that either candidate will arrive at the convention with enough pledged delegates to win the nomination,” Weaver said during an interview on ABC News’ “Powerhouse Politics” podcast.

Even though the majority of superdelegates are expected to vote for Clinton, Weaver noted that "those people are not pledged when they get there" and believes that they will "take a second look” at Sanders because, in November, “these people want to win.”