People gather at the U.S.-Mexico border fence to talk to relatives in Playas de Tijuana, on the outskirts Tijuana, in northwestern Mexico, in July. (Guillermo Arias/AFP via Getty Images)

Can Donald Trump actually keep his pledge to build a southern border wall?

Build that wall! Build that wall!” was a favorite chant at Trump campaign rallies. As a real estate developer, this would be his most impressive construction job. As he said early in his campaign, “I would build a great wall, and nobody builds walls better than me, believe me, and I build them very inexpensively.”

Critics were as dismissive of Trump’s wall as they were of Trump as a presidential candidate. The wall proposal, they said, was nothing more than a political fantasy.

But under President Trump, the wall will not only be for real, but it may be one of his biggest political successes. Here’s how.

Whatever is built or is already there, Trump will call it a wall

Words matter. When one thinks of a wall, one thinks of something solid — which, no doubt, is part of its enormous political appeal for Trump supporters. But the term “wall” is actually surprisingly fuzzy. The various Oxford dictionary definitions of a wall include “any high vertical surface, especially one that is imposing in scale.” That broad definition would seem to leave Trump a lot of wiggle room.

It is important to remember that Trump’s predecessors carefully avoided calling any new border barriers a “wall.” Before Trump, the term was politically taboo, viewed as sending the wrong message to Mexico and to the world. When Pat Buchanan ran for president in 1996, he proposed building a “sea wall” to stop the “tidal wave” of illegal immigration across the border — and was dismissed as an extremist and ostracized by the Republican Party.

But times have changed. Trump broke the taboo. His fans have loved him for it. So regardless of what Trump ends up building, calling it a “wall” will sound like something new and make his followers cheer.

Much of the wall has already been built

Since the early 1990s, politicians of all stripes have scrambled to show their commitment to border security. During that time, annual federal funding for border and immigration control mushroomed from $1.5 billion to $19.5 billion. According to one estimate, Washington spends $5 billion more on border and immigration control than for all other federal law enforcement combined.

And the result? Hundreds of miles of metal barriers have gone up. Technologies initially developed for the military have been adapted for border enforcement. A fleet of manned and unmanned aircraft have been deployed to monitor from the air. Thousands of new agents have been hired. The size of the Border Patrol doubled in the 1990s and has more than doubled again since the beginning of the century, from about 4,000 personnel to more than 21,000.

This massive enforcement buildup has been lethal for many migrants trying to cross, with thousands of deaths to date, while enriching the smugglers on whom migrants must rely. As I showed in my book “Border Games: Policing the U.S. Mexico Divide,” it has been politically rewarding for both Democrats and Republicans alike. Trump is simply taking it to the next level.

Trump has dismissed the current state of border security as “a joke,” but he’ll soon find that the bipartisan border policing boom started in the 1990s will be crucial to keeping his wall pledge. Trump’s plan calls for a wall that covers 1,000 miles of the nearly 2,000-mile-long border — with natural obstacles covering the remainder. Nearly 700 miles of various types of border fencing are already in place, and portions of it very much look like a formidable metal wall. It is hard to imagine Trump tearing all that fencing up and starting from scratch.

What’s much more realistic is that Trump will simply add more miles of fencing; reinforce existing fencing in key, visible places; and deploy even more border guards, stadium lighting, and the latest high-tech detection and surveillance equipment. The newest, tallest part of the Trump Wall — probably erected at one of the most visible, urban spots on the border — would be an effective backdrop for the president’s celebratory news conference announcing its construction.

In the end, Trump’s wall is likely to be the latest addition to the border barrier-building frenzy first launched by President Bill Clinton, greatly expanded by George W. Bush and continued by Obama. But Trump will take full ownership of it as the only president willing to actually call it a wall.

It will not stop migrants from entering the country illegally — going over, under or around it, with many of them dying in the process. But when Trump supporters grumble that the wall is too porous, Trump will no doubt promise to make the wall even longer, taller and stronger in his second term.

Peter Andreas is the John Hay Professor of International Studies at Brown University’s Watson Institute. His new book, “Rebel Mother: My Childhood Chasing the Revolution,” will be published in April by Simon & Schuster.