WASHINGTON — Ten of the many Democrats seeking their party’s 2020 presidential nomination debated in Miami Wednesday night in a two-hour nationally televised event. In one sense, the practical winner was not on the stage: former Vice President Joe Biden.

As the contestants vied for air time, they eschewed taking on Biden and used the small windows afforded them to introduce themselves and their political policies to the public.

The result was a mish-mash of self-promotion via NBC, CNN and Telemundo, with a gaggle of talking heads posing questions and getting brief answers.

In a sense, Biden’s free ride devoid of attacks on him as the frontrunner validated his early campaign decision to identify himself as the prime Democratic vehicle for combatting Donald Trump in 2020. He embraced the role while others focused on filling the void in their own resumes.

The most prominent Democrat in the first round, Sen. Elizabeth Warren of Massachusetts, distinguished herself with a temperate, lucid shopping list of policy positions, placing herself solidly within the growing Democratic realm of progressivism.

She advocated expanding the social-welfare agenda, notably with so-called Medicare for All replacing President Obama’s Affordable Care Act. She thus positioned herself in opposition to Biden, who favors ACA and maintenance of the private insurance industry through which many workers now are covered.

Organized labor, to whom Biden has been a longtime champion and defender, has been a strong ally, and his 2020 campaign is grounded in his self-identification as Mr. Blue Collar America. He has underscored his strength in the industrial Rust Belt states that gave Trump his Electoral College victory in 2016.

In Wednesday night’s event, three other Democrats sought greater support by challenging others on the stage. Sen. Cory Booker of New Jersey and former Rep. Beto O’Rourke of Texas trotted out their Spanish linguistic skills in answering questions, as did former Obama cabinet official Julian Castro.

Sen. Amy Klobuchar of Wisconsin essentially hewed to the same moderately liberal path trod by Biden in his 36 years in the Senate eight as vice president. She too defended maintaining private insurance for those provided it through their employers.

In all, the Democratic National Committee’s earnest attempt to be fair to all by putting so many candidates on a single stage provided a poor version of a genuine debate. Eventually, the dilemma will be resolved by the inevitability of a field narrowed as support and campaign assets wither for fading contenders.

At least two more rounds of these multiple quasi-debates via television are scheduled for July and August. Then will come the selection of national convention delegates in many state caucuses and primaries, starting in Iowa and New Hampshire early in 2020, along with more manageable televised debates.

When it comes to presidential debates, one longs for the standard set in the Kennedy-Nixon debates of nearly 60 years ago when cool and unflabbergasted JFK took the measure of sweating Tricky Dick under the studio lights in Chicago, and eked out a narrow trip to the Oval Office.

In the intervening years, presidential debates have been ducked by some presidents, including Nixon in 1968. Clinging to a narrow lead in the polls over the Democratic nominee, Vice President Hubert Humphrey, Nixon declined to debate and survived in an election shrouded to his day in controversy over the Vietnam War.

In 1976, President Gerald Ford fumbled a question against Democratic nominee Jimmy Carter by erroneously saying: “There is no Soviet domination of Eastern Europe, and there never will be under a Ford administration.” Many critics attributed his loss to it.

In 1984, Vice President Walter Mondale lost his presidential bid against President Ronald Reagan after the older former movie star joked in their debate: “I will not make age an issue in this campaign. I am not going to exploit for political purposes my opponent’s youth and inexperience.”

Presidential elections of course should not hang on such trivialities. Debates remain essential today, but should not be reduced to frivolous showcases by their overseers to satisfy candidates’ demands for more and more free air time.

Editor’s note: Jules Witcover’s latest book is “The American Vice Presidency: From Irrelevance to Power,” published by Smithsonian Books. You can respond to this column at juleswitcovercomcast.net.