The signature sentence of this election begins with the words “In a country of 320 million . . .” I hear it everywhere. It ends with “how’d it come down to these two?” or “why’d we get them?”

Another sentence is a now a common greeting among Republicans who haven’t seen each other in a while: “What are we gonna do?”

The most arresting sentence of the week came from a sophisticated Manhattan man friendly with all sides. I asked if he knows what he’ll do in November. “I know exactly,” he said with some spirit. “I will be one of the 40 million who will deny, the day after the election, that they voted for him. But I will.”

A high elected official, a Republican, got a faraway look when I asked what he thought was going to happen. “This is the unpollable election,” he said. People don’t want to tell you who they’re for. A lot aren’t sure. A lot don’t want to be pressed.

That’s exactly what I’ve seen the past few weeks in North Carolina, New Jersey, Tennessee and Minnesota.

Every four years I ask people if they’ll vote, and if they have a sense of how. Every four years they tell me—assertively or shyly, confidently or tentatively. This year is different. I’ve never seen people so nervous to answer. It’s so unlike America, this reticence, even defensiveness. It’s as if there’s a feeling that to declare who you’re for is to invite others to inspect your soul.

“I feel like this is the most controversial election ever,” said a food-court worker at La Guardia Airport. She works a full shift, 4 a.m. to noon, five days a week, then goes full-time to a nearby college. We’d been chatting a while, and when I asked the question she told me, carefully, that she hasn’t decided how she’ll vote, and neither have her family members. I said a lot of people seem nervous to say. She said: “Especially Trump people. They’re afraid you’ll think they’re stupid.”

Which is how I knew she was going to vote for Donald Trump.

It’s true: Trump voters especially don’t want to be categorized, judged, thought stupid—racist, sexist, Islamophobic, you name it. When most of them know, actually, that they’re not.

Voters who talk about 2016 are very careful to damn both sides, air their disappointment, note that they’ve been following the election closely. They know each candidate’s history.

In Tennessee I asked a smart businessman who he’s for. He carefully and at length outlined his criticisms and concerns regarding both candidates. Then, as I started to leave, he threw in, from nowhere: “So I think Trump.”

When I talk to strangers—which I do a lot, and like it—I sometimes say dour, mordant things, to get them going by establishing that anything can be said. I say if Hillary Clinton is elected there will be at least one special prosecutor, maybe two, within 18 months, because her character will not be reborn on crossing the threshold of the White House; the well-worn grooves of her essential nature will kick in. If Mr. Trump is elected there will be a constitutional crisis within 18 months because he doesn’t really know what a president does, doesn’t respect traditional boundaries, doesn’t reflect on implications and effects. I always expect pushback. I am not getting it! I get nods, laughs and, in two recent cases, admissions that whoever wins they’d been wondering how soon impeachment proceedings would begin.

Oh, my pained and crazy country.

A final observation, underlying all. Under the smiles and beyond the reticence it is clear how seriously Americans are taking their decision, how gravely. As if it’s not Tweedledum and Tweedledee but an actual choice between two vastly different dramas, two different worlds of outcome and meaning. The cynic or the screwball? Shall we go to the bad place or the crazy place?

I returned knowing I was wrong about something. I thought everyone has been watching the election more than a year, everyone knows their opinion of Mrs. Clinton and Mr. Trump, this thing is pretty much settled. No, it’s fluid. This cake is not baked.

I talked to Peter D. Hart, the veteran Democratic pollster. Are things as much in play as I think? Yes and no, he said. People do have a firm opinion of the two candidates, the clichés are set: “Hillary competent and cold, Trump an incompetent loose cannon.” But “the part that is evolving is a sense of what we need to do and where we need to go.” Everyone wants change, but people are deciding, “constructive change or radical change?”

Pollster Glen Bolger of Public Opinion Strategies says nothing is settled. “Voters are angry at Clinton because she can’t tell the truth and they’re scared of Trump because they’re afraid he’s gonna start a war. There are times her un-truthiness outweighs their concern about him overreacting and starting a war. It goes back and forth.”

He disagrees with the “unpollable” premise: “It’s pollable. But if anyone says their results are cast in concrete, that’s a mistake. There’s a lot of fluidity.”

The veteran pollster Kellyanne Conway, now Trump campaign manager, says: “This thing is fluid in a way we don’t understand.” She is a close student of Barack Obama’s 2008 campaign in all its aspects. Like Mr. Obama, she says, Mr. Trump is “a candidate built for the 21st century. . . . The most fundamental truth of politics is there’s no substitute for a great, magnetic, compelling candidate.”

She speaks of “undercover” Trump voters. “To call them hidden is a mistake. They’re undercover because they’ve gotten to the point they’re tired of arguing. . . . Some have been voting Democratic all their life, they voted for Obama, they’re tired of defending and explaining themselves” to family and coworkers. “They don’t want to proselytize.”

Mr. Hart said the debates are unusually important this year. “Trump is the central character—it’s his last opportunity to get a fresh look from voters. A debate is an open window. Voters suspend opinions and look afresh. Attitudes toward Trump have not changed—temperament questions, can he do the job?” This is a chance for him to “establish credibility at this stage of the game.” By contrast, “Hillary’s problems are not professional but personal—can I like her, does she understand me. . . . It’s an opportunity for her to get voters saying, ‘You know something, she’s not a bad egg.’ ”

Ms. Conway too says the debates are key. “People like a clash of the titans. They like a contest. These debates are the ultimate reality show—the stakes have never been higher.” After the Democratic convention the Clinton campaign, in a major miscalculation, “lowered the bar” for Trump, “calling him unfit, unpresidential.” That turned him into the underdog. “Americans love an underdog.”

Ms. Conway remembered what happened in 2008 when John McCain referred to his long experience. “Obama said if experience means you got us into this mess overseas and tanked the economy, maybe experience is overrated. We are turning this around on Clinton now.”

Mr. Trump’s advantage? “Americans love to say they think outside the box. Trump lives outside the box. Hillary is the box.”