(CNN) Every four years, political nerds -- like me! -- raise the possibility that one of the two major parties will head into the national convention without one candidate having secured a majority of delegates to be the presidential nominee, forcing an all-out floor fight for the right to represent the party on the presidential ballot.

But the truth is that it almost never happens -- for a lot of reasons but mostly because the parties live in fear of a chaotic nominating process hamstringing their eventual nominees and costing them the White House.

In fact, it's been almost four decades -- 1984 -- since either party went into its national convention without a single candidate having secured the required number of delegates to be the nominee . That year Walter Mondale was just a few dozen short of the number and, despite Gary Hart's best efforts, the Minnesota senator won the nomination on the first ballot.

To find the last truly contested convention -- one in which multiple ballots were required to pick the nominee -- you have to go all the way back to 1952, when Adlai Stevenson secured the Democratic nomination on the third ballot.

So when people talk brokered or contested convention, I am usually very skeptical. Except that in the 2020 Democratic race, absolutely every sign is beginning to point to just that outcome.

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