As he does at nearly all his rallies, Donald Trump made a dramatic promise to thousands of his followers at a recent event here.

“We’re going to build a wall, and it’s going to be a real wall — it’s going to be a wall that’s going to make that ceiling look quite low, and it’s fairly high,” Trump said, gripping the sides of his lectern and gazing up at the ceiling of this city’s convention center as the crowd roared with laughter and applause. “And it’s going to get built fast, and it’s going to look beautiful because someday they’ll call it the Trump Wall. Who the hell knows?”

The wall along the Mexican border is one of Trump’s most enduring and popular proposals, prompting raucous cheering and chants wherever he goes. Yet many of Trump’s fans don’t actually think he will build a wall — and they don’t care if he doesn’t.

Many also don’t think that Trump as president would really ban foreign Muslims from entering the country, seize oil controlled by terrorists or deport 11 million illegal immigrants. They view Trump’s pledges more as malleable symbols than concrete promises, reflecting a willingness to shake things up and to be bold.

“Trump says a lot of things right off the cuff. Does he mean it to the ‘T’? I don’t think so,” said Dennis Kerns, 55, a retired ­elementary-school teacher who lives near Albuquerque and came to the rally with his wife. “When he talks about bombing ISIS and all of that — his advisers aren’t going to let him go off half-cocked and bomb here and bomb there.”

Here are some of the most memorable campaign promises Republican presidential candidate Donald Trump has made since he declared his candidacy in June 2015. (Sarah Parnass/The Washington Post)

He added: “I think if he strengthens the borders . . . it will be the same as building the wall. So the wall’s still there, it’s just invisible. It might be 10 feet tall, it might be 20 feet tall, but it’s invisible. So the wall can be built even without having to be built.”

Perhaps more than any other presidential candidate in history, Trump has mastered the art of putting forth a platform that is so vague — and so outlandish — that supporters can believe what they want to believe about his plans, even when it comes to something such as a concrete wall on the southern border.

A Fox News poll last month found that 66 percent of Trump’s supporters believed that he would build a wall, while the rest didn’t think it would happen or had no opinion. Of all those polled, about half expect Trump to follow through on his promises to build the wall or to deport millions of undocumented immigrants, and 58 percent believe he will ban most foreign Muslims from entering the country.

The ambiguity presents a stark challenge for his probable opponent in the general election, Hillary Clinton: How can she and other Democrats convince people that Trump’s ideas are dangerous if many voters don’t believe he will actually implement them?

Trump has repeatedly insisted that he is not joking about constructing a wall, and he has offered up specifics: He will construct it out of hardened concrete, rebar and steel, and it will be taller than any ladder and one foot taller than the Great Wall of China. He and his staff composed a briefing document earlier this year laying out how he would compel Mexico pay for the wall.

But Trump has also said at times that many of his proposals — including the wall and a temporary ban on allowing most foreign Muslims into the country — are merely “suggestions” that are open to negotiation. He has reduced the wall to a punch line at his campaign rallies, often asking crowds who will pay for it and getting a booming, laughing response: “Mexico!”

Ian Carney, who works in construction and came to the Albuquerque rally with his girlfriend, described the wall as simply a “rhetorical device” that Trump uses.

Donald Trump's latest attack on the "Mexican" judge overseeing his Trump University case has left his surrogates scrambling to defend his remarks. Here are some of their attempts at defending him. (Monica Akhtar/The Washington Post)

“Personally, I think it’s symbolic. I mean, a physical wall?” said Carney, 26. “It’s just such a strong vision and idea, but I just care about the border being secure.”

Mindy Kruichak, a 50-year-old corporate consultant sitting in the stands, said the whole wall idea is “maybe a little cray-cray,” but if anyone can accomplish this, it’s Trump — although she says he should first fix the health-care system and wipe out socialism.

One true believer in the Albuquerque crowd was David Buck, a 56-year-old contractor who has only three expectations for Trump’s first year in office: “building that damn wall,” making Mexico pay for it and lowering taxes.

“We’ve got too many drugs coming through, we have too many illegal aliens jamming up our schools and our hospitals, our welfare systems,” Buck said. “So, yeah, I want that wall.”

Trump has often taken both sides of an issue, even on proposals central to his campaign.

When it comes to war, Trump has said that he is opposed to spending billions of dollars fighting other country’s problems — but that he also will “bomb the hell out of ISIS” and seize oil controlled by terrorist groups. When it comes to abortion, he has said that he will appoint only “pro-life” judges to the Supreme Court, and a televangelist who often speaks at Trump’s rallies has declared that the candidate would “abolish” abortion — but Trump has also come to the defense of Planned Parenthood and was once unabashedly in favor of abortion rights. When it comes to taxes, Trump has said that wealthy individuals like himself need to pay more — but he has also denied saying that and released a tax proposal calling for major decreases for all taxpayers, including the very rich.

When asked in an interview last month what he plans to do to clear up such discrepancies, Trump said there is no need to do so.

“I mean, I feel that I’m very consistent — but you must have flexibility,” Trump said. “If you have a position, that doesn’t mean that there is not a better alternative, and you can’t have. I’ve dealt with people over the years that are totally inflexible, and they’re never successful. A lot of times things are subject to flexibility and change.”

At a spate of recent rallies in the West, audience after audience laughed and applauded as Trump promised to build them a wall. Sometimes they burst into a chant: “Build that wall! Build that wall!”

“I actually believe him,” said Colleen Bellitti, 46, a beauty-products creator who lives in the Los Angeles area and pulled her son out of school so they could attend a rally in Anaheim, Calif. “I actually think he’s going to do it. I actually think he’s going to come out with a vengeance. I really do.”

The next evening in Billings, Mont., Bret Weddle said he expected Trump to build a wall in some places but not across the entire 1,989-mile border. An easier way to protect the border, he said, is to increase the number of Border Patrol officials, ensure that employers are checking the residency status of their workers and stop providing free government services to those who enter the country illegally.

“Virtual fences,” said Weddle, 40, a father of two who works as an IT consultant.

The next morning in Fresno, Calif., Ruth Pendergrass said that although she wants countries to have clear and distinct borders, building a wall “is not something that’s a priority to me.” She would rather see Trump first repair the country’s crumbling roads and build up its infrastructure, while better enforcing immigration laws already on the books.

“I don’t see what building a wall is going to do, because they build tunnels underneath,” said Pendergrass, 55, a grandmother of two who used to work in a pharmacy and came to the rally with her sister. “Maybe he intends on really building one — I don’t know that — but I think he’s just trying to set his tone that we have to separate the countries.”

On the other side of the arena that morning was Brock Lechowicz, a 29-year-old wearing a red “Make America Great Again” hat who shifted in his seat when asked what he thought of Trump’s proposal to build a wall.

“So, I like to believe that a lot of that is just maybe, like, some political marketing,” said Lechowicz, who sells industrial supplies to hospitals and came to the rally with a friend. “I see where he’s coming from with it, but it’s not like there’s not already something like a wall there, and it’s not like bills and such haven’t been proposed previously. But I would take it more as political marketing — I think he’s making a stand and wants to be a little bit more outrageous with it to draw attention to the ideology that he wants to stand for things that people aren’t standing for. And, honestly, I think he’s a marketing genius.”

Scott Clement in Washington contributed to this report.