By 2020 will Biden, Bernie, Beto bust?

Promise me something: Over the coming weeks, whenever you hear a pundit or read a poll on the subject of who the 2020 Democratic nominee might be, you’ll flash back four years. You’ll remember predictions about the Republican nominee at this same point before the 2016 election.

Republicans then were in a situation similar to the one that Democrats are in now. More than a dozen candidates were poised to run. And in December 2014, CNN/ORC published the results of a survey that sought to determine which of them had the most support and the best chance.

The answer was not Donald Trump.

“Jeb Bush is the clear Republican presidential front-runner, surging to the front of the potential GOP pack,” read the story on CNN’s website. Surging. Jeb!

He had the support of 23 percent of respondents. That put him fully 10 points ahead of his nearest competitor, who was ... Chris Christie. Next came Ben Carson, followed by Rand Paul and Mike Huckabee.

Need I remind anyone how that fearsome five fared?

We political junkies got far ahead of ourselves then, and we’re getting ahead of ourselves now. Almost 23 months before the 2020 election, we’re handicapping contenders, edging toward prophecies and setting ourselves up to look every bit as foolish as we deserve to.

Polls are being done at an accelerating pace. CNN released one late last week. It surveyed Democratic voters nationwide, among whom Joe Biden ranked first; Bernie Sanders, second; and Beto O’Rourke, third. So they’re the Bush, Christie and Carson analogues. If 2014 is any guide, they should spare themselves a lot of travel and a world of heartache and pack it in now.

Of course, 2014 isn’t a guide, but it’s a reality check. Assessments of candidates at this early stage have limited bearing on how well they’ll be doing more than a year down the road, when the Iowa caucuses kick off the primary season.

At this juncture back then, Trump’s candidacy wasn’t even anticipated. Pollsters didn’t present his name to Republican voters as an option. He came onto the radar and earned inclusion in polls around May 2015, but he didn’t immediately take the lead. In a Quinnipiac poll of Republican voters released on May 28, 2015, he placed eighth, just behind Ted Cruz. Cruz would be the only one, in the end, to give him any competition for the nomination.

Sure, most of the candidates have been vetted somewhat during prior runs for office. But whatever scrutiny they received pales next to the withering spotlight of a presidential bid.

We think we know a lot about these candidates, and we do. But we don’t have the most consequential information of all. We haven’t heard the specific, boiled-down cases for themselves — and their prescriptions for the country’s future — that they’ll present to voters. We don’t know how persuasively they’ll communicate that. And we haven’t been able to judge how well it complements what voters are hungriest for now.

Trump is instructive. The phenomenon of his candidacy had everything to do with what he said when he came down that escalator in Trump Tower on June 16, 2015.

Biden’s, Sanders’ and O’Rourke’s strong showing in current polls isn’t wholly irrelevant. It will help them with fundraising and direct more media attention their way. I was joking when I suggested that it spelled doom.

But they shouldn’t be too encouraged by it. And the rest of us shouldn’t use it to write off other candidates.