Democratic presidential candidate Marianne Williamson in Washington on Aug. 21. (Andrew Harrer/Bloomberg News)
Data analyst and political columnist

The huge number of contenders for the 2020 Democratic presidential nomination has provided a summer’s worth of amusement. But, despite how the 2016 Republican primary contest unfolded, politics aren’t supposed to function like reality television — with bizarre characters thrown into the mix for the sheer sake of drama. So it’s puzzling that the Democratic National Committee appears to be losing its nerve and abandoning a smart, well-designed plan to use its debates to winnow the field.

Amazingly enough, there are still 20 “major” candidates in the field, which makes the field too big to function. Fitting all of them into a debate takes two nights. Listening to each of them talk for just six minutes back to back would take two hours. Even highly engaged voters in Iowa, who have more contact with candidates than almost any other Americans, can’t pick all of them out of a lineup.

This unwieldiness might be worth it if the huge field were genuinely in flux, but it’s not. Historical data shows that candidates who are polling at roughly zero percent at this point in the campaign almost never win their party’s nomination — so about 10 of these candidates have little to no chance of winning. Yet they’re sticking around. And while contenders such as Marianne Williamson and Andrew Yang are adding new ideas to the conversation, they’re not exactly upending the debate.

The Democratic Party likely doesn’t want these candidates to continue. But as candidates have gained the ability to fund their campaigns through small-dollar donations and use national and social media to broadcast their message directly to people, the party has lost the ability to force them out. That leaves the debate qualification rules as one of the few tools the party has left to declare who is serious, and who is merely using the process as a brand-building exercise.

The original approach seemed to revolve around a simple principle: Give nearly everyone an opportunity to shine in the early going, but then thin the field by slowly shifting focus to top-tier contenders. Candidates didn’t need to do much to qualify for the first two debates — they just had to get to 1 percent in three different polls and get donations from 65,000 people across 20 states. That’s not a heavy lift for a presidential campaign, and 20 candidates made it into both debates.

In the third debate, scheduled for next Thursday, the DNC raised the polling and fundraising bar just a little bit, and 10 candidates — a smaller but still pretty large group — qualified. The process was basically working: The field started to slowly narrow as candidates such as Kirsten Gillibrand, Eric Swalwell, John Hickenlooper and Jay Inslee failed to make their mark in the debates and dropped out. Candidates such as Amy Klobuchar and Cory Booker, who have small followings and a small but real chance of winning, will be on the same stage as poll leaders Joe Biden and Elizabeth Warren. But the Tim Ryans of the field will have to stay home.

But for some reason, Democrats are shying away from this plan. All 10 candidates who have qualified for the third debate will be onstage for the fourth debate in October, while Marianne Williamson, Tom Steyer, Tulsi Gabbard and others who failed to hit the polling and fundraising thresholds for the third debate will have a chance to make it, as well. According to Politico, it’s likely that more candidates will participate in the fourth debate than the third.

This is a mistake. The DNC should use its power to squeeze bottom-tier candidates. At this point in the campaign, it’s not useful to hear Bill de Blasio self-promote for 10 minutes. That time is far better spent trying to get Warren and Biden to engage with each other on economic issues, or to see Klobuchar spar with Bernie Sanders over whether far-left idealism or liberal pragmatism is the future of the party. Splitting the top contenders between two nights and giving part of the time to John Delaney helps no one, except maybe Delaney.

The DNC can’t make everyone happy when they’re designing the debates. In a field this large, someone is going to get left off the stage and blame the DNC — rather than themselves — for failing to meet the qualifications. But the debate rules exist to help the party’s rank and file pick a candidate who both represents them effectively and can beat President Trump, not to help Joe Sestak build his self-esteem.

Read more:

Paul Waldman: Why Democratic ideas will dominate the 2020 campaign

Ed Rogers: Will Trump’s behavior decide the 2020 election?

Jonathan Capehart: Democrats want to beat Trump. Biden wants to be the one to do it.

Jennifer Rubin: Maybe Democrats should run on overwhelmingly popular issues

Amanda Ripley: How to redesign the debates for our current political climate