David R. Wheeler is a freelance writer and a journalism professor at the University of Tampa. Follow him on Twitter @WheelerWorkshop . The opinions expressed in this commentary are solely those of the author. View more opinion articles on CNN.

(CNN) The list of people defying President Donald Trump gets longer by the minute. But one voice rose above all the others last week. Retired Navy Adm. William H. McRaven penned an op-ed in the Washington Post asking Trump to revoke his security clearance, so he can add his name "to the list of men and women who have spoken up against your presidency."

Why is this a big deal, you ask? After all, many top government officials from both parties have condemned Trump.

Here's why: McRaven is not your average admiral. As commander of the US Joint Special Operations Command (JSOC) from 2008 to 2011 and US Special Operations Command (USSOCOM) from 2011-2014, McRaven oversaw the Navy SEAL mission in Pakistan that killed al Qaeda leader Osama bin Laden and its impact..

If Democrats want a trump card against Trump, they should consider McRaven as a candidate for the presidency in 2020. For one thing, he's an actual American hero. When it comes to the military, Trump blusters or throws tantrums at or about them. But McRaven took out targets. That's a contrast that would work decisively in McRaven's favor.

But to really understand why McRaven could be the ideal candidate to oppose Trump in 2020, let's go back to 2016. That year, during the Republican primaries, the question on everybody's mind was which establishment candidate with actual government experience would win the nomination. Would it be Gentle Jeb Bush? Mundane Marco Rubio? Stodgy Scott Walker? Few imagined the answer would be Disquieting Donald Trump, the "outsider" real-estate developer. But from a field of safe picks, the self-styled populist candidate emerged, unexpectedly, victorious.

JUST WATCHED Ret. Lt. Gen. to Trump: Take my clearance too Replay More Videos ... MUST WATCH Ret. Lt. Gen. to Trump: Take my clearance too 01:45

That, along with the impressive showing of democratic socialist Bernie Sanders, made it clear: In politics, populism has become the name of the game in America.

And with democratic socialist candidate Alexandria Ocasio-Cortez's stunning upset over 10-term Democrat Joe Crowley in New York's 14th Congressional District in June, many Democrats are convinced they need to field a presidential candidate from the populist left to fire up the base in 2020.

But what if the unexpected happens again — this time on the Democratic side? What if, from a crowded field of populists such as, say, the senators Elizabeth Warren, Cory Booker, and Bernie Sanders, an establishment Democrat emerges, instead, with the nomination in 2020? If that happens, it could be because McRaven throws his white Navy admiral hat into the ring. Imagine it: Trump vs. McRaven.

Some rather somber statistics from June's Gallup Poll explain why McRaven's background is ideal -- not because he is a populist (he isn't) but because he is unexpected. In our bitterly polarized era, only 37% of the public expresses a "great deal" of confidence in the presidency. A whopping 44% express "very little" or "none." When it comes to the church and organized religion, only 38% of Americans have a "great deal" of confidence in those institutions.

JUST WATCHED Clapper: McRaven is a personal hero of mine Replay More Videos ... MUST WATCH Clapper: McRaven is a personal hero of mine 02:20

Meanwhile, the percentage of Americans who have a "great deal" of confidence in Congress is barely out of the single digits.

But one institution rises high above the rest, with no other even coming close. That institution is the military, with 74% of the country expressing a "great deal" of confidence in the armed services, and 20% expressing "some" confidence. Only 5% have "very little" or "none." In this ranking, small business is a distant second, and the police come in third.

Historically, a background in the military has been an asset for a presidential candidate. Of the 44 men who have served as president, 31 of them (about 70%) served in the military before becoming commander in chief, according to the American Legion. Although the traditional military-vet candidate is Republican (think John McCain), more Democratic veterans, especially women, are running -- and winning.

Trump ascended to the White House thanks to about 80,000 votes scattered across the traditionally Democratic states of Michigan, Pennsylvania and Wisconsin. With Trump's currently dismal approval rating -- despite a roaring economy -- couldn't Democrats win those votes back?

They might be able to if they choose a candidate with a background that nearly everyone respects. Despite uneven progress in Iraq and Afghanistan, there's one military operation that Americans across the spectrum herald as an undisputed success: the raid that killed Osama bin Laden. In fact, Americans approved so highly of that operation that Barack Obama, who was president at the time, saw his approval rating rise instantly by six points.

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(McRaven, by the way, isn't the only one saying he'd be honored if Trump would revoke his clearance, too -- he appears to have started a trend. Former CIA and NSA Director Michael Hayden told CNN he'd be fine having his security clearance revoked, too, after Jake Tapper asked him about McRaven's op-ed.)

It's not surprising that, as Trump bungles nearly everything he touches on the planet, he daydreams more and more about space. Meanwhile, McRaven can point to accomplishments right here on Earth.

A previous version of this op-ed incorrectly identified William McRaven as commander of US Joint Special Operations Command (JSOC) from 2011 to 2014. During those years, he was commander of US Special Operations Command (USSOCOM), of which JSOC (which McRaven commanded from 2008 to 2011) is a component command.