People are not always great at predicting their own behavior. We know what we think and feel in the moment, but are much less effective at guessing how we will respond to different conditions in the future.

I see this all the time as a pollster who thinks about how to ask people questions that will reveal how they genuinely think and feel. If you ask me what I am doing right now, I would say I am writing this essay — and that would be an accurate response. If you ask me whether I would make pasta for dinner later this week if I knew that pasta sauce was going on sale at the grocery store, my answer would be less accurate. Am I even going to want pasta?

Similarly, if you ask voters how they feel today about Donald Trump, trust me — they know. Voters’ attitudes toward Mr. Trump and his personal character have been long established. But asking voters what they might do in the future given an unprecedented change in circumstances, like a major presidential candidate being sentenced to time in prison, is fraught with uncertainty.

As a result, one of my biggest pet peeves as a pollster is the “more or less likely” survey question. In this type of question, respondents are asked if a certain hypothetical situation or piece of information would make them “more or less likely” to take a future action. This is often used to test campaign and political messaging strategy and takes the form of “If you knew that Candidate A voted to raise taxes, would that make you more or less likely to vote for him?”

In the Trump legal dramas, this type of question has been a pollster favorite, with resulting takeaways like this one last week: “One in 10 Republicans Less Likely to Vote for Trump After Guilty Verdict.” Whenever I see that kind of headline, I wonder if those one-in-10 Republicans were ever voting for Mr. Trump anyway, or were they “Never Trump” Republicans who had already been leaning to President Biden and were now simply even more firm in their defection? These sorts of things matter greatly when it comes to gauging whether the verdict is having a material effect on the race.

The still-imperfect but far better way to measure the impact of some new development is to see if people have actually changed their voting intentions. It turns out that so far, in the wake of Mr. Trump’s conviction on 34 felony counts of falsifying business records, not very many people have. My firm asked almost 500 voters nationwide in the day after the verdict whom they’d vote for and whether the verdict had changed their votes. The catch? We had already surveyed those people in the last few months, so we knew what they’d told us earlier.

When we asked these voters whom they intended to vote for, 97 percent of those who had previously said they’d vote for Mr. Trump in 2024 stayed with Mr. Trump. Similarly, 98 percent of those who had previously said they’d vote for Mr. Biden stayed with Mr. Biden. The best news for Mr. Biden is that, among the extremely small number who had previously reported being undecided, 40 percent say they are now leaning Mr. Biden’s way, with only 3 percent of previously undecided voters switching to Mr. Trump.

When we then specifically asked these respondents if the verdict had caused them to switch their vote, almost none of the respondents who said they switched because of the verdict had in fact changed their vote away from Trump or Biden from the earlier survey.

The guilty verdict, in and of itself, does not seem to actually be moving voters in the short term. People who previously believed Mr. Trump was a good man or worthy of being president still think so. People who previously disliked him have had their views affirmed. Impressions of Mr. Trump are so powerfully ingrained, it would take something even more monumental than being found guilty of falsifying business records to change it.

But I think it is too soon to throw up our hands and declare that this all doesn’t matter politically. I believe that if Mr. Trump is given a sentence involving prison time that could shape the race.

“Trump is a convicted felon” is a statement about who he is as a person — corrupt, rule-breaking, dishonest — which is something that people already have firm opinions about. “Trump is going to prison” is a development of a different nature, an elevation of the severity of the situation and what a Trump presidency might mean for the country beyond simply “Trump is a bad man.”

If Justice Juan Merchan sentences Mr. Trump to probation, community service or some other lesser punishment, the effect of the trial will be whether people feel uncomfortable choosing as president someone who also bears the label of felon. Early data suggests that the label alone is not a game-changer. Voters who lean toward Mr. Trump may well conclude that having to check in with a probation officer periodically won’t impede his performance as commander in chief.

Prison is different. The reality is that most voters are not anticipating that Mr. Trump will actually face incarceration. In my data, only one in five thinks he is likely to get prison time, and most of those are already Biden voters. It isn’t hard to imagine a voter who isn’t crazy about Mr. Trump but leans toward voting for him, who thinks the trial and verdict itself were much ado about nothing, yet when confronted with the prospect of voting for a man who has been sentenced to prison has a strong reaction.

This reaction to the sentence could cut both ways. Most obviously, voters who are reluctantly considering Mr. Trump could determine that sending someone to the White House at the same time he is facing prison is a bridge too far. Less likely but not impossibly, a harsh sentence could harden the resolve of those disaffected Republicans who have a distaste for Mr. Trump but nevertheless feel he’s been treated unfairly in this case.

That Mr. Trump might be heading to prison is something most undecided and Trump voters have not priced into their assumptions about the presidential race. That immediately makes the situation much more volatile.

Which raises the worrisome prospect of the second-order effects a tough sentence could have on the nation, and the race. Mr. Trump has ominously warned of a “breaking point” if he is sentenced to prison. Clearly, the verdict alone, absent sentencing, has rallied Mr. Trump’s most staunch supporters; he raised $53 million in donations in just the 24 hours following the verdict. But it is unsettling to consider what a prison sentence might mean in a political environment in which Trump supporters feel that our system of government itself is on the brink as a result of the trials and verdict. (Few things have moved the polls on Mr. Trump in a major way, but one did, at least temporarily: the violent scenes of Jan. 6.)

Mr. Trump’s sentencing is set for just days before he is formally nominated as the Republican candidate for president. We have historical precedent for knowing what a “convention bump” looks like in the polls, but we do not have any precedent for knowing how voters might react to a major presidential candidate being sentenced.

Be wary of any confident declarations of what Mr. Trump’s guilty verdict means for the election over the next few weeks. The sentence, not just the verdict, will determine the ultimate effect the case has on the election.