While there are literally dozens of Democratic presidential candidates, only five have been able to make a dent in the competitive race for the 2020 nomination.

By all realistic measurements such as polling and fundraising, Joe Biden, Bernie Sanders, Elizabeth Warren, Kamala Harris, Pete Buttigieg have consistently stayed at the top of the field.

Other candidates are stuck fighting tooth and nail to register at just one or two percent in order to qualify for the debate stage.

It loosely resembles the 2016 Republican presidential primary, in which the field narrowed dramatically to only a few candidates shortly after voting began.

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The field of Democratic presidential candidates all vying to unseat President Donald Trump from the White House in 2020 is historically massive. While there are 24 legitimate candidates, it is more or less a five-candidate race by all realistic measurements: Joe Biden, Bernie Sanders, Elizabeth Warren, Kamala Harris, and Pete Buttigieg.

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What each poll shows, whether in a national scope or narrowed down to specific early voting states, is that only a few candidates emerge at the top of the field, while the remaining dozen-and-a-half candidates barely crack 1%.

Consistently, each poll paints a similar picture in which Biden holds a commanding lead, which has slimmed down a bit since he underwhelmed at the first primary debate in Miami, followed by a mix of Harris, Sanders, and the resurgent Warren. Buttigieg has maintained a strong showing after emerging from obscurity into an unlikely frontrunner.

No candidate has overtaken Biden in the RealClearPolitics polling average. None surpassed Sanders until this month, when both Warren and Harris received a post-debate bump.

Buttigieg hovers above 5% as well, which is light years ahead of the rest of the field struggling to get the mandatory 2% in four separate Democratic National Committee-approved polls before the August debates. Former Rep. Beto O'Rourke of Texas started quite strong, but in recent months has seen any traction all but evaporated.

It can be seen in fundraising hauls as well, with elite candidates raking in multimillion dollar hauls each quarter while the rest fight for just enough donors to qualify for a spot on the primetime debate stage.

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And the upcoming fall debates have much more strict criteria compared to the first two. Candidates will have to achieve 2% in four separate DNC-approved polls and receive 130,000 individual donations and 400 donors in at least 20 states or US territories.

When the bottom dozen or so candidates cannot even crack 1% in most polls, the prospect of building a following to cultivate tens of thousands of donations becomes quite bleak. And getting cut from the debates could easily be a death sentence for an already fledgling campaign.

There's still time for candidates in the rear of the field to generate a polling surge should they have a breakout performance in a debate or garner attention through other means. But the field is already shaping up to be one that has a top tier and a much more crowded bottom tier.

The 2016 Republican presidential primary played out in a similar fashion.

There were 16 total candidates all told, but just a few led the pack for the run of the race. When voting finally began, it became clear the field was only really comprised of Trump, Sen. Ted Cruz of Texas, Sen. Marco Rubio of Florida, and then-Ohio Gov. John Kasich.

A lot can happen between now and the first caucuses and primaries in early 2020. But if the top five Democrats maintain their dominance among both donors and polling, it could quickly mirror the 2016 Republican race, where more than a dozen presidential hopefuls burnt through cash and traversed the country only to drop out once the voters' disinterest was registered at the ballot box.