It occurred to someone at Gallup, wisely, that if Donald Trump is the most poorly viewed major-party presidential candidate of all time and if Hillary Clinton is in second, there must be some overlap between those two groups. That is: There must be a large number of people who view both Trump and Clinton unfavorably.

And so there are. By Gallup's estimate, a full one-quarter of American adults view both Trump and Clinton unfavorably — a figure that's more than twice as high as those who disliked both Mitt Romney and Barack Obama in 2012.

Only 4 percent of Americans viewed both Trump and Clinton favorably. Everyone else fell into the camps you'd expect: Liking one candidate and disliking the other.

We went back and looked at our own data to see how this might have changed over time. Interestingly, the percentage of respondents to Post/ABC News polls who say they dislike both has been fairly constant, usually just over 20 percent. The percentage who view both positively has declined over time. (In that first poll, from May 2015, Trump was broadly disliked, so the percentage of people that viewed him favorably, regardless of how they felt about Clinton, was small.)

Who are these people that dislike both candidates? According to Gallup, more than half are independents, which makes sense. They also tend to be younger, suggesting that there may be some overlap here with supporters of Bernie Sanders. (The Gallup data pre-dates Sanders's endorsement of Clinton.)

It's possible, then, that the upper-right quadrant of the top graph may grow, as Clinton gains support at Trump's expense. It's possible, too, that we'll need to add a third dimension to the chart, showing, somehow, Americans' feelings about a third-party alternative to the two least-popular candidates on record.