There are reasons to be skeptical that the wall on the border would ever be built. Putting a ban on Muslims entering the country seems neither practical nor constitutional.

But Donald Trump has finally made one three-word campaign promise that voters may be able to count on.

“I’m not changing,” he declared this week.

Indeed, it is the rest of the political world that is having to adjust.

If recent days are any indication, the remaining five months of this presidential campaign are likely to be fought entirely on Trump’s terms.

The celebrity real estate mogul continues to defy predictions — including some of his own — that he will soften his rhetoric and elevate it to a more presidential level as he moves into a general-election campaign.

His adversaries are now adopting his tactics, even as Trump himself is intensifying and broadening his attacks.

Democratic nominee-in-waiting Hillary Clinton, not usually known for her zingers, delivered a speech that was positively Trumpian in the volume of insults she aimed at the man who will be at the top of the GOP ticket.

“Donald Trump’s ideas aren’t just different — they are dangerously incoherent,” Clinton said. “They’re not really ideas, just a series of bizarre rants, personal feuds and outright lies.”

Meanwhile, even as she was speaking, a Tweet arrived from House Speaker Paul D. Ryan (R-Wis.) announcing that the Hamlet of Janesville has come to terms with what pretty much everyone else knew was inevitable.

“I’ll be voting for @realDonaldTrump this fall. I’m confident he will help turn the House GOP’s agenda into laws,” Ryan wrote.

That second sentence was the rationalization. The reality was that Ryan had capitulated, having earlier insisted that he could not support Trump unless he “advances the principles of our party and appeals to a wide, vast majority of Americans.”

Speaking at a rally in Redding, Calif., Republican presidential candidate Donald Trump pointed out a man at the rally and said, "look at my African American." Trump then mentioned an African American supporter who punched a Trump protester dressed like a Ku Klux Klan member at an Arizona rally in March. (Reuters)

Trump did not budge, so Ryan had to.

The speaker’s endorsement ended his awkward standoff with the man who will be his party’s nominee. But it put Ryan into another kind of difficult position, which is having to answer for everything that Trump has to say.

Senate Majority Leader Mitch McConnell (R-Ky.) told CNN that he fears that Trump’s bombast will become a trademark for the entire party, much as 1964 GOP nominee Barry Goldwater’s vote against the Civil Rights Act that year did.

“It did define our party, for at least African American voters, and it still does today,” McConnell said. “That was a complete shift that occurred that year and we’ve never been able to get them back.”

McConnell urged Trump to be more conciliatory now that he has all but won the GOP nomination.

“I think the attacks that he’s routinely engaged in — for example, going after Susana Martinez, the Republican governor of New Mexico, the chairman of the Republican Governors’ Association — I think, was a big mistake,” McConnell said.

“What he ought to be doing now is trying to unify the party and I think attacking people once you have won — it’s a time, if you can, to be gracious and to try and bring the party together,” McConnell added.

So far, however, the closest that Trump has come to that was announcing that he would recycle the nickname “Lyin’ Ted,” which he had applied to his GOP rival Sen. Ted Cruz of Texas, and apply it to “Lyin’ Hillary.”

Republican leaders are also worried that Trump is further alienating important constituencies.

In an interview Thursday with the Wall Street Journal, Trump stepped up his attacks on the federal judge presiding over lawsuits against one of his endeavors, the now-defunct Trump University, suggesting that Indiana-born Gonzalo Curiel should be taken off the case because he has Mexican roots.

“I’m building a wall. It’s an inherent conflict of interest,” Trump said.

On Friday, in an interview with CNN’s Jake Tapper, Trump refused to back down when Tapper suggested that his objection to Curiel was “the definition of racism.”

“But he’s an American. He’s an American,” Tapper said of the judge.

“He’s of Mexican heritage, he’s proud of it,” Trump replied.

So much for reaching out to Latino voters — an effort so futile for the GOP at this point that the Republican National Committee’s Hispanic media director, Ruth Guerra, resigned this week. Sources said it was because she was fed up.

Her replacement, Helen Aguirre Ferré, who has a history of negative comments about Trump, had to scrub her Twitter account. She deleted one Tweet sent less than a month ago, in which she predicted that Trump would drive Miami’s Cuban Americans from the Republican Party.

Ryan, fresh from having endorsed Trump, expressed dismay over the presumptive nominee’s comments about the judge, which he told a Wisconsin radio station were “out of left field for my mind.”

“It’s reasoning I don’t relate to,” Ryan said in an interview with 1130 WISN. “I completely disagree with the thinking behind that.”

Early on, Trump was criticized for seeming to encourage violence by his supporters at his rallies.

But Thursday night, it appeared that the other side had been inspired to do the same — and more — in San Jose.

Anti-Trump protesters pelted his supporters with eggs and water balloons, snatched their “Make America Great Again” hats, and burned them. Some were even caught on camera punching people for the offense of having shown up at a Trump rally.

In an interview on CNN, Clinton said she condemns “all violence in our political arena,” but she blamed Trump for setting the tone.

“He set a very bad example. He created an environment in which it seemed to be acceptable for someone running for president to be inciting violence,” Clinton said. “Trump has lowered the bar, and now is it a surprise that people who don’t like him are stepping over that low bar? I don’t think it is.”

“I don’t think any of this helps anybody,” she added.

All of this has had the predictable effect on Trump himself.

During Clinton’s address, she noted wryly that she supposed that Trump was composing tweets about her at that very moment.

And sure enough, he was: “Bad performance by Crooked Hillary Clinton! Reading poorly from the teleprompter! She doesn’t even look presidential.”

But he was just getting warmed up.

“Remember I said I was a ­counter-puncher?” Trump said in San Jose. “I am. After what she said about me today and her phony speech. That was a phony speech. That was a Donald Trump hit job. I will say this. Hillary Clinton has to go to jail. She has to go to jail.”

And this is only the beginning of the general-election season. There are still more than 150 vitriolic days to go.