The latest Post/ABC News poll has some good news for Democrats, and some bad news for President Trump: In head-to-head matchups, Joe Biden beats the president by 15 percentage points; Bernie Sanders beats him by nine points; Elizabeth Warren and Kamala D. Harris both beat him by seven points; and Pete Buttigieg beats him by four.

There’s a reasonable and common response to results such as these, which is that these polls don’t tell us anything this far from the election. But why is that? What will change between now and next November?

The short answer is: For Trump, very little. For Democrats, almost everything.

Perhaps the most important fact about Americans’ opinions about Trump is how stable they are. No matter what bizarre and appalling things he does, they don’t move very much; his approval ratings have stayed within a few percentage points of 40 percent for nearly the entirety of his presidency.

We see that in this newest Post/ABC poll, as well: Trump gets 40 percent against Biden, 43 percent against Sanders, 44 percent against Warren, 43 percent against Harris, and so on. His support doesn’t change much no matter who he’s matched up against, but some voters move in and out of the “undecided” column depending on the matchup — which suggests that the difference between how well each Democrat is doing right now has a lot to do with voter familiarity.

And that makes sense. If you’re a political junkie, you may have a clear idea of what Warren or Buttigieg is about. But, for lots of voters, they have only a few vague impressions from a story or two they saw either on the news or in a Facebook ad that came across their screens.

That’s the first reason that things are going to change: Most voters still haven’t gotten to know the Democratic candidates in any meaningful way. The second reason is that events will occur on the campaign trail that are impossible to predict.

We can pretty much guarantee that one or more of the candidates will confront some sort of scandal — or at least an intense controversy. Perhaps it’ll be because of something they say, or some part of their past that diligent opposition researchers uncover. It might be completely legitimate, or it might be utterly bogus. We just don’t know.

How they react to it — whether they show the skill and fortitude to overcome it or it drags them down — will tell us a lot about what kind of candidates they are. But just about every presidential candidate confronts that kind of situation at some point. Trump had the “Access Hollywood” tape. Barack Obama had the controversy over his pastor. George W. Bush had the revelation of hidden drunken-driving arrests. Bill Clinton had Gennifer Flowers’s allegation of an affair.

Each of those scandals had its own character, but what they have in common is that the candidate was able to get past them. In fact, you could argue that there’s no better indicator of “electability” than a candidate’s ability to deal with controversy. Unfortunately, it doesn’t provide a primary voter much basis to judge when the candidates have yet to be tested in that way.

Biden, for instance, touts his early polls against Trump in his first ad in Iowa, but his first run for president imploded when he was shown to have plagiarized a British politician in his speeches. What did the former vice president learn from that, and would he be better able to deal with the next scandal when it hits? We can guess, but we can’t know for sure.

That’s to say nothing of how Biden or any other candidate will handle the frenzy of the general election, particularly when Trump — quite possibly with the help of the Kremlin and who knows who else — creates an atmosphere of chaos and madness in which all notions of objective truth become meaningless. And once Republicans unleash a white-hot campaign of hate and fear against the Democratic nominee, opinions about them will polarize. You think Republicans dislike those Democratic candidates now? Just you wait.

There are also real-world events that could shape the general election, from an economic downturn to foreign crises to mass shootings (the last one is all but assured; the only question is how many there will be and how many Americans will be slaughtered).

But all of that probably won’t affect how Americans view Trump, except at the margins. By now, people know who he is and what they think about him, and when he runs another race-baiting campaign and we learn more about his corruption, those opinions are unlikely to change. And as the election approaches, a healthy number of Republicans who now tell pollsters they don’t like him will move into his camp anyway, because the campaign will activate their partisan attachments and dislike of Democrats. There will be some defectors (and we can argue about which Democrat is most likely to win more of them), but their numbers will be small.

All of which means that we’re now still in the cone of uncertainty. We can make educated guesses about what the next 14 months hold, but educated guesses is all they are.

Read more:

Robert Gebelhoff: Here’s how social media could threaten democracy — even without the help of Russians

Josh Rogin: Bolton lost the latest Trump administration factional battle, but not the last

Dana Milbank: This is how the Trump administration quietly incapacitates the government

David Von Drehle: Trump’s jazz combo of national distraction gets some new members