So here’s another simple rule to evaluate presidential polls going forward. Call it the 80-55-40 Rule: Since 1980, no Democratic presidential candidate has won less than 80 percent of blacks; 55 percent of Hispanics; or 40 percent of whites. (A tiny exception: In 1992, Clinton got 39 percent of the white vote, and Bush got 40 percent; Perot did exceptionally well among white voters.)

Here are the exit-poll breakdowns of the five most recent elections.

It would be nice to call this the 80-60-40 Rule, but history doesn’t always cooperate with heuristics. Democrats won less than 60 percent of Hispanic support twice since 1980, with Carter in 1980 (56 percent) and Kerry in 2004 (56 percent).

How should one use the 80-55-40 rule? Look at today’s poll, which has Clinton winning just 52 percent of Latinos. Following the 80-55-40 rule, this should raise a tiny red flag. Donald Trump has accused a Mexican American judge of putting his family’s heritage above the law, repeatedly promised to build a wall to keep out Mexicans, opened his candidacy by declaring “they’re rapists, and some, I assume, are good people,” and reached out to undecided Latinos by posing next to a taco salad.

Is it possible that Trump could break with recent precedent, and win a historically high share of Hispanic voters? Yes, under certain quantum-theory conditions, all sorts of things are possible: Time can move backwards, tornados can build neighborhoods from pieces of homes floating in the sky, and a cracked egg can leap into its original unbroken shell. But unless you think that “the Hispanics” love Trump as much as he swears he loves them, you might want to question the poll.

The 80-55-40 Rule doesn’t mean that you should automatically reject every poll showing Hillary Clinton receiving, for example, just 75 percent support from blacks. You can choose to believe that number. But such a belief must live side-by-side with recent history. Since 1980, no Republican candidate has won more than 12 percent of the black vote. So for Trump to win, say, 20 percent of black voters, it means that a candidate drawing unprecedentedly public support from white nationalists is doing twice as well among black voters as any GOP candidate in modern history.

Does that make any sense? Well, it’s a democracy. You decide.