While Joe Biden is out to a massive lead in the primary polling, it’s still far too early to say who will still be standing when the voting begins next year. But if there’s one thing all of the Democratic primary voters appear to agree on it’s that the eventual nominee needs to be the most electable. But what does that even mean? The Washington Post’s Dan Balz took a stab at the question this week, prompting quite a bit of discussion among the commentariat. His eventual conclusion was that we’re not only lacking a good definition of the concept, but we frequently don’t even know it when we see it. For proof, look no further than the beginning of the 2016 and 2008 races.

Four years ago at this moment, almost no one, except perhaps the man himself, believed that Donald Trump was electable. He wasn’t even a formal candidate, after all. Although he had been on the edge of the political stage, conventional wisdom afforded him little chance of becoming the 45th president. On the electability scale, he was in the low range.

Twelve years ago at this time, Hillary Clinton was judged to be the most-electable Democrat seeking the nomination. A New York senator, former first lady and part of the then-best brand in Democratic politics, she had the attributes that added up to being most electable.

So we, as a nation, tend to get the electability question wrong on a regular basis. That attribute is, at best, a very intangible thing and it’s based, as Balz says, on our own inherent beliefs, prejudices and biases. For a slightly different take, check out what Doug Mataconis had to say about it in response.

When pundits have pondered this issue in the past, they’ve typically focused on things such as a candidates resume. This is why many people believed that Richard Nixon was more “electable” than John F. Kennedy, that George H.W. Bush seemed like the more natural candidate for President over Ronald Reagan in 1980, and that Ted Kennedy seemed like he could make history and become the first candidate in the modern era to defeat an incumbent President in a primary battle.

In each of these elections and more, though, it turned out that it was the candidate who people thought was not electable that ended up winning the election. Indeed, of all the elections going back to 1968 one could argue that the only time the “electable” candidate won was Richard Nixon in 1968 and 1972 and George H.W. Bush in 1988. Every other time it’s seemingly been the upstart or “surprise” candidate who has ended up winning the election.

We can argue all day about various elections in the past and which candidate “looked” more electable on paper, but there’s no reference point for us to go by – even after the fact – to base predictions on. The fact is that there is no metric for electability. It’s something that can only be observed after the fact. We can try to point to polling data as some sort of electability index, but it’s an inexact science at best. Remember that nearly every polling outfit had Hillary Clinton winning the last presidential election right up until the end of October. But in the end, her actual electability turned out to be zero while Donald Trump’s was 100%.

As far as I’m concerned, any given candidate’s true electability is, as one famous Secretary of Defense once said, a known unknown. But I do have a guess as to why we’re so prone to getting the question wrong. It’s the undeniable tendency of human beings to assume that most other people see things the way they do, or at least that they would do so if given sufficient evidence. “How are reasonable people not going to vote for Candidate X when they’re so obviously the best choice?”

But reasonable people may, in fact, feel the same way about Candidate Y and turn out to be wondering what the heck is wrong with you. All of this is based on one assumption that I’m fairly sure holds true. Nearly everyone winds up supporting someone they believe can win if given the chance. (I’m speaking mostly about the primaries here.) You may like, admire and respect a candidate, but if you don’t believe they can make it over the finish line, why put your support behind them? Of course, when it comes to the general election, most registered Democrats and Republicans will follow their party’s nominee and leave it to the independents to decide the winner.

But none of this helps us when we’re looking at a field the size of the current Democratic primary crew. We still can’t say for sure which one of them can win their own party’s nomination, to say nothing of their chances of beating Donald Trump next year. Okay… I’ll make one exception to that statement. You can rule of Bill de Blasio. That guy’s not going to win anything outside of New York.