Donald Trump speaks at a campaign event at Trump Doral golf course in Miami.

Donald Trump speaks at a campaign event at Trump Doral golf course in Miami. Carlo Allegri/Reuters

Businessman Donald Trump officially became the Republican nominee at the party’s convention in Cleveland.

It was a bad time for Sen. Cory Gardner to be caught in an elevator with a reporter. Donald Trump had just referred to Sen. Elizabeth Warren of Massachusetts as ­“Pocahontas” — again — and the Republican freshman from Colorado was struggling to figure out how to respond.

“I think people need to be treated with respect, and that’s what we’ve demanded from everyone,” he offered.

But was it racist?

Gardner clammed up. He politely referred further questions to his press secretary.

So it went for Republicans on Capitol Hill on Friday, forced to contend with yet another provocative comment by their presumptive presidential nominee — clambering for safety as Trump launched another boundary-pushing attack.

[In Florida, Trump attacks rivals — and not just the Democrats]

“Get used to it,” said Republican pollster Whit Ayres, a Trump critic. “This is your life for the next five months.”

The furor over Trump’s assaults on the impartiality of a Latino judge had just begun to subside when he lobbed two tweets Friday morning responding to Warren, who had lambasted him as a “thin-skinned, racist bully” in a speech the previous evening.

“Pocahontas is at it again!” Trump wrote in one. “Goofy Elizabeth Warren, one of the least productive U.S. Senators, has a nasty mouth.”

“No, seriously — Delete your account,” Warren tweeted back. One of the senator’s supporters secured Pocahontas.com and redirected it to Warren’s campaign site.

[Elizabeth Warren, Joe Biden lead coordinated Democratic attack on Donald Trump]

The real estate developer has repeatedly invoked the ­17th-century Native American figure to refer to Warren, an allusion to controversy about her heritage. The senator has said she grew up amid family stories about her Cherokee lineage, but that account has not been proved.

Presumptive Republican nominee Donald Trump took aim at Sen. Elizabeth Warren (D-Mass.) at a rally in Tampa, Fla., on June 11. He called Warren "Pocahontas," a jab at her claim that she is of Native American descent. (Reuters)

Trump began going after Warren’s claimed ancestry earlier this year, responding to the senator’s repeated slams of him as a “loser” and a bully. “Who’s that, the Indian?” he said at a March news conference when asked about Warren. “You mean the Indian?”

His swipes at her have intensified as the senator has emerged as one of his fiercest adversaries. On Thursday, she endorsed presumptive Democratic nominee Hillary Clinton, and the two women met privately on Friday.

The latest gibes come amid a weeks-long uproar over Trump’s repeated criticism of U.S. District Judge Gonzalo Curiel as biased and unfair because of his Mexican heritage. The claim drew a storm of denunciation, including a strong rebuke from House Speaker Paul D. Ryan (R-Wis.), who called it “the textbook definition of a racist comment.”

By comparison, the response to the Pocahontas remarks have been mixed and in many cases muted — a sign of how jittery GOP leaders are still trying to find their comfort level with his rhetoric.

“Oh, I think it’s done in good humor,” said Sen. Roger Wicker (R-Miss.), who heads the National Republican Senatorial Committee, the organization charged with electing Republican senators in 2016.

Sen. Lindsey O. Graham (R-S.C.), normally a ferocious Trump foe, was similarly unfazed.

“It’s pretty funny, I thought,” Graham said. “I think what he said about the judge was racist. When you’re talking about a politician, you got to be able to take a joke. . . . If this bothers you, you need to get out of politics.”

But others were alarmed.

“He needs to quit using language like that,” said Rep. Tom Cole (R-Okla.), a member of the Chickasaw tribe and one of two Native Americans in the House. “It’s pejorative , and you know, there’s plenty of things that he can disagree with Elizabeth Warren over, this is not something that should, in my opinion, ever enter the conversation. . . . It’s neither appropriate personally toward her, and frankly, it offends a much larger group of people. So, I wish he would avoid that.”

Sen. John McCain (R-Ariz.), who is up for reelection in a state with one of the highest proportions of Native Americans in the country, also chastised Trump.

“I just don’t engage in personal insults — that is a personal insult,” he said.

[As he moves campaign to battlegrounds, which Donald Trump will show up?]

The “Pocahontas” line spurred chatter at former Massachusetts governor Mitt Romney’s ideas summit Friday in Park City, Utah, where some attendees said they were aghast at Trump’s many race-based lines of attack.

Stuart Stevens — the chief strategist on Romney’s 2012 presidential bid, who, like Romney, has vowed not to vote for Trump — said the candidate’s use of “Pocahontas” to attack Warren was both racist and inappropriate.

“If you said this in a sixth-grade class, the teacher would tell you, ‘Don’t say this,’ ” Stevens said.

“This is a sick guy, and Americans are not longing for a president who’s going to go out and use ethnic slurs against people,” he said. “It’s amusing in the same way telling dirty jokes around a frat house can get laughs, but most people grow out of that. It’s childish.”

Romney told CNN on Friday that he was worried Trump’s language could lead to “trickle-down racism” in the country.

When asked why he persists in calling Warren “Pocahontas” and what he makes of the alarm it has caused among some Republicans, Trump responded bluntly in a statement Friday: “Because she is a nasty person, a terrible U.S. Senator, and it drives her crazy.”

“The Republicans should find it offensive that she scammed the system by faking her heritage, not that I am unafraid to point that out,” he continued in the statement, which was provided by his spokeswoman, Hope Hicks. “Actually, Goofy Elizabeth, her nickname, is far worse.”

Pocahontas is the nickname of the daughter of a Powhatan chief who was kidnapped by the English about 1613. She converted to Christianity and married an Englishman, a union that is credited with bringing a lull to hostilities between the settlers and American Indian tribes. Her story inspired the popular 1995 Disney animated film of the same name, furthering perceptions of Pocahontas as a princess, although historians say much of what has been written about her is a romanticized legend at odds with the hardships she endured.

Stephanie Fryberg, an associate professor of psychology and American Indian studies at the University of Washington, said her studies have found that exposing Native American children to images of Pocahontas lowered their sense of collective self-worth.

“Mr. Trump’s comments reinforce broad stereotypes of Native Americans as Indian chiefs, mascots and princesses, rather than contemporary people who are contributing to society,” she said, adding: “He’s not using the term in any way to be honorific. He using it to mock her.”

Trump has repeatedly rejected the notion that he is playing to racial fears in his campaign. “I am the least-racist person that you’ve ever encountered,” he told The Washington Post on Thursday.

Trump has been accused of peddling Native American stereotypes in the past. In 1993, he created an uproar at a House subcommittee hearing by testifying that “organized crime is rampant” in Indian casinos around the nation. At the time, the developer was fighting the expansion of gambling on tribal lands, a direct threat to his casino empire.

Ditching a seven-page statement he planned to deliver as too “politically correct,” Trump claimed that he could keep mobsters out of casinos but that Native Americans would not be able to.

“That an Indian chief is going to tell Joe Killer to please get off his reservation is almost unbelievable to me,” he said, prompting objections from lawmakers and indignant scoffs from the audience.

Trump also questioned the legitimacy of the Mashantucket Pequots, who operate the Foxwoods Resort Casino in Connecticut.

“They don’t look like Indians to me,” he said. “And they don’t look like Indians to Indians.”

In 2000, he secretly financed newspaper ads in Upstate New York warning that a casino sought by the St. Regis Mohawk nation would attract criminals and drug users.

This spring, Trump has repeatedly tweeted about Warren’s ­“phony Native American heritage.” He tried out the Pocahontas line in a May interview with New York Times columnist Maureen Dowd, who had asked about his feud with Warren. “You mean Pocahontas?” he replied.

[Donald Trump just called Elizabeth Warren ‘the Indian.’ Here’s what that’s all about.]

He has continued to refer to her as “Pocahontas” on the campaign trail since then. A Cree reporter in North Dakota chastised him for use of the name, declaring, “That’s very offensive!”

On Friday, Trump’s latest barrage left many Republican leaders squirming.

Sen. Susan Collins (R-Maine) ignored a question about his use of the name, delivering instead a long explanation about why she had to turn her attention back to a discussion about trade issues.

“I’m not going to enter into the daily visitation” of Trump’s comments, said Sen. Bob Corker (R-Tenn.), chairman of the Senate Foreign Relations Committee, who warned earlier this week that the real estate mogul has a dwindling amount of time left to elevate the tenor of his campaign.

For his part, Sen. John Barrasso (R-Wyo.) said he was withholding judgment. “I haven’t seen it,” he said of Trump’s tweet. “Until I see something, I’m very careful.”

Paul Kane in Washington and Philip Rucker in Park City contributed to this report.