Voters and pundits might struggle with Democrats’ policy positions in the 2020 campaign, but it’s remarkable how swiftly they lock in the names.

Bernie is always “Bernie,” not “Sanders,” yet Warren is “Warren,” not “Liz.” Pete is “Pete,” never “Buttigieg.” But Booker? He’s not “Cory.”

Democrats are awaiting a decision by “Joe.” If Biden does run, he’ll join a crowded field that includes “Beto” (never O’Rourke) and “Harris” (rarely Kamala).

They all want a crack at the guy who for decades was known as The Donald — a label first given him by former wife Ivana — until he ran for president and decided to be “Trump.” This wouldn’t work for most candidates. Erica Castro, for example, is unlikely to want her husband to be known as The Julian. And John Bessler wouldn’t care to have his wife, Sen. Klobuchar, referred to as The Amy.

Besides, “Klobuchar” doesn’t work on T-shirts the way “Amy for America” does. An even worse fit would be “Hickenlooper,” although America might also be underwhelmed by “John for President” — which is why odds for the former Colorado governor are longer than his last name.

Obama was the rare politician who succeeded despite the curse of a name Madison Avenue didn’t love. “Barack for President” was not pleasing, and “Hussein for President” would have been worse. BHO never clicked. Depending on your orientation, it’s Butane Hash Oil or the symbol for Raja Bhoj Airport in India.

For a while, however, initials were the rage. We had JFK and then LBJ, and, of course, the simplest initial of all for a man whose very being was rooted in simplicity: W.

As for first names names, they work in showbiz (think Cher, Oprah, Clint, et al), but not so well in politics. Presidential hopefuls Beto, Bernie, Pete, Amy and Joe would presumably seek to avoid comparisons with one of history’s best known mononymous candidates, Hillary (“please don’t call me Clinton”).

Truth is, Americans have never much cared for presidential candidates who went by their first names. Honest Abe was a notable exception, but Lincoln’s time was back in 1860. It wasn’t until 1948 when someone else managed to run successfully on a first-name basis: “I’m just wild about Harry” was Truman’s slogan, along with the also popular “Give ‘em hell, Harry.”

Four years later Dwight David Eisenhower used the bumper-sticker-friendly phrase “I like Ike” to cruise into the White House, making him the nation’s last first-name president.

Some in the current Democratic field are still trying to figure out where they fit name wise. The New York senator’s site is “Gillibrand 2020,” but her official bio refers to her as “Kirsten” a total of 10 times without once invoking the name “Gillibrand.”

And then there is Sen. Harris. As the California Democrat’s popularity grows she might choose to become just “Kamala.” In her book she says it means “lotus flower,” which, she notes, “is a symbol of significance in Indian culture.”

For others, it’s simply first name or bust. After all, no matter what you think of Bernie, you’ll admit that “Feel the Sanders” just wouldn’t fly.

Peter Funt is a writer and speaker. His book, “Cautiously Optimistic,” is available at Amazon.com and CandidCamera.com.