President Trump listens as he and NATO Secretary General Jens Stoltenberg participate in a news conference in the East Room of the White House on April 12 . (Jabin Botsford/The Washington Post)

Remember the very first episode of “Black Mirror,” the one in which the prime minister of the United Kingdom is extorted into doing … something he would rather not have done? He woke up that morning just a regular ol’ prime minister and by midafternoon he’d ended up cheating on his wife, sort of.

If you haven’t seen it, it doesn’t matter. You just need to know that, as the prime minister was weighing his options over the course of the day, he was being constantly updated on how the public was viewing the rapid-fire shifts in the decision-making process. At the outset, he was viewed positively. When his aides tried to get him out of the problem, his numbers tanked. In other words, there were multiple polls conducted over the course of the day that informed whether he would have sex with a pig on live television.

Oh. Spoilers.

The point is that this is not the speed at which polling works. There are snap polls that can be conducted after things such as important speeches, but those are generally organized in advance. There are Internet-based polls that can offer insights faster than traditional phone-based polling, but even those generally aren’t conducted over the course of hours. What this means is that getting evolving insights into breaking news is very tricky, and getting solid poll data on recent events is similarly difficult to pull off.

Sometimes, though, there’s a crack of light. As we got this week, with a new poll from Monmouth University.

Monmouth was in the field (that is, interviewing poll respondents) for a survey as news broke on Monday night that President Trump had revealed classified information in an Oval Office conversation with Russian Foreign Minister Sergey Lavrov. They’d started polling on Saturday night and continued the polling through Wednesday and, conveniently, were already asking people about the subject at hand: Trump’s relationship with Russia.

The result? We get some indication of how those attitudes changed. Granted, since we’re splitting the pool of responses in half, the margins of error are larger than for the overall poll numbers. But on three Russia-related questions, attitudes shifted against Trump in the latter half of the polling.

On the question of whether an independent investigator should be appointed, the percentage of people favoring such a move shot up by eight points later in the week. (The pollsters note that the actual appointment of special counsel happened after the vast majority of surveys.)

On the question of whether people were concerned that Trump was too friendly to Russia, the percentage saying they were concerned a lot increased eight points. Attitudes on the question of whether Trump’s attitude toward Russia posed a national security risk flipped, with a plurality saying “no” over the weekend and a majority saying “yes” after the news broke.

But here’s the thing: It doesn’t seem to have affected Trump’s approval rating. Before the news broke, he was at 39 percent approval. After? The same. The percent who disapproved had increased, but that’s it.

Thirty-nine percent is a bit under where Trump is in the RealClearPolitics average of approval polls (which includes that Monmouth number). After the missile strike in Syria, his numbers, which had been slipping, started to rise again. At the beginning of May, they began to drop again. They’re now at their lowest point.

We spend a lot of time focused on whether Trump’s base — a big chunk of that 39 percent — is going to abandon him. That’s probably the wrong question. The question is whether he can add to that percentage. The recent news didn’t erode that base, but it may have helped solidify opinions against him.

It’s a long time until 2020, and these numbers will change. But couple the recent news casting Trump’s administration in an unfavorable light with these low approval numbers, and the real danger is exposed: Trump can’t use his popularity as a cudgel to keep Congress in line. Not just on policy, but on avoiding repercussions from his actions such as censure or impeachment, should it come to that.

One of the main reasons, by the way, that it’s good that polling takes a while is that it builds in some distance from whatever happened, giving us a less-reactionary response. So although Monmouth’s polling is evocative, polling in the future probably will offer us more useful information.

Unlike that poor guy from “Black Mirror,” we have the luxury of waiting for it.