A growing number of Republican lawmakers and strategists fear that Donald Trump’s hostile remarks about minorities and his un­or­tho­dox strategy have imperiled his campaign at the end of a five-week head start on Democratic front-runner Hillary Clinton that they hoped would fortify him heading into the general election.

Their concerns increased again Sunday after Trump said he thought a Muslim judge might treat him unfairly because he wants to temporarily ban most foreign Muslims from entering the country. The remark was an expansion on repeated assertions over the past week that an American-born judge overseeing a fraud case against him should recuse himself because of his “Mexican heritage.”

“If it were a Muslim judge, would you also feel like they wouldn’t be able to treat you fairly because of that policy of yours?” host John Dickerson asked on CBS’s “Face the Nation.”

“It’s possible, yes. Yeah. That would be possible, absolutely,” Trump replied.

While Republicans credit Trump for making some strides after vanquishing his final GOP opponents last month, many are concerned about repeated comments singling out people for criticism on the basis of race, ethnicity or religion. The attacks in the Trump University case also underscore the extent to which Trump, who is traveling overseas later this month to visit some of his golf courses, commingles his private business interests with his presidential campaign.

The campaign of the presumptive Republican nominee, Donald Trump, is sparking a surge in the number of citizenship applications and voter registrations among Hispanics fearful of his immigration policies. Since January, California alone has seen a boost of 218 percent in Democratic registration and among Hispanics, registration is up 123 percent. (Alice Li/The Washington Post)

Finally, many Republicans are also unnerved by Trump’s decision to continue picking fights with fellow Republicans and to spend time and resources campaigning in California and other Democratic-leaning states that he is extremely unlikely to win in November.

The prevailing view among prominent Republicans is that Trump still has the time and ability to make the necessary course corrections, especially given Clinton’s vulnerabilities. But they see some acute problems in the way he has conducted himself in recent days.

Republican strategist Brian Walsh, a former spokesman for the National Republican Senatorial Committee, quickly took to social media after Trump’s remarks on Muslims on Sunday: “I don’t care if he’s the nominee — Republicans should loudly condemn this racist, nonsensical rhetoric by Trump,” Walsh tweeted.

Walsh, who does not support Trump at the moment, said in an interview that Republican leaders should not hesitate to condemn comments that are “the definition of racism.”

“It’s very toxic for other Republican campaigns and for the party as a whole,” he said. “It’s very concerning.”

In the latest sign of the separation down-ballot Republicans are seeking from Trump, Sen. Kelly Ayotte (N.H.) responded to Trump’s latest comments with a strongly worded statement to The Washington Post.

Republicans and Democrats alike are slamming Donald Trump for his comments about a federal judge. Here are six times something Trump said made sparked a huge backlash from critics. (Sarah Parnass/The Washington Post)

“His comments are offensive and wrong and he should retract them,” said Ayotte, who is in a challenging reelection campaign.

Trump’s remark on a theoretical Muslim judge followed his repeated comments arguing that U.S. District Judge Gonzalo Curiel, who is presiding over fraud lawsuits against his Trump ­University education business, should have recused himself because “he’s a Mexican.” Trump says his desire to build a wall on the border with Mexico was in conflict with the judge’s ethnic background; Curiel was born in Indiana to Mexican immigrant parents.

Republican leaders, including House Speaker Paul D. Ryan (Wis.) and Senate Majority Leader Mitch McConnell (Ky.), who both support Trump, have criticized those statements.

“I couldn’t disagree more with a statement like that,” McConnell said on NBC’s “Meet the Press,” though he repeatedly refused to say whether the comments were by definition racist.

Former House speaker Newt Gingrich, another Trump booster, also criticized him on “Fox News Sunday.”

“This is one of the worst mistakes Trump has made, and I think it’s inexcusable,” said Gingrich. He added: “If a liberal were to attack Justice Clarence Thomas on the grounds that he’s black, we would all go crazy.”

Rep. Tom Cole (R-Okla.), a longtime party strategist and Trump supporter, said in an interview that the real estate mogul needs to “move from a primary message to more of a general-election message” and “to start trying to find ways to reach out to groups he doesn’t need to win, but he needs to make sure he’s not annihilated among,” such as African Americans and Hispanics.

Trump has consistently struggled throughout his campaign with both his rhetoric and policies relating to minorities. At a rally in Redding, Calif., on Friday, Trump pointed to a black man in the crowd and exclaimed, “Oh, look at my African American over here — look at him.”

“It seems the campaign has been a tad slow to a full transition to a general-election strategy,” said Greg Mueller, who has worked on several presidential campaigns and backs Trump. “But they have time and a bully pulpit like few other Republican candidates in recent times.”

Rick Wilson, a longtime GOP operative who has been one of the most aggressive critics of Trump, penned a column to fellow Republicans this weekend warning that candidates up for election will be yoked to Trump: “You own his politics. You own his policies, even the ones that only last as long as the next contradiction. You own the racial animus that started out as a bug, became a feature and is now the defining characteristic of his campaign. You own every crazy, vile chunk of word vomit that spews from his mouth.”

Wilson said in an interview Sunday that Trump’s comments about Curiel and a hypothetical Muslim judge are “overtly racist” and contradict the freedoms outlined in the Constitution. Wilson said that it is “mortifying” that Trump would use a judge’s ethnic heritage as an excuse for why Trump University has lost court decisions.

“For everyone who cries wolf on racism — and there are a lot of them on the other side — they are now validated forever,” Wilson said.

Republican concerns over Trump’s campaign extend beyond his comments to his strategy. After cementing his claim to the nomination after the May 3 Indiana primary, Trump has taken long stretches off the trail and, when he is campaigning, has focused his time on blue states that still have primaries to come but are virtually unwinnable for a Republican in the general election. California, where Trump held rallies over the past two weeks, was last won by a Republican nominee in 1988 by George H.W. Bush; a recent survey showed Clinton with a double-digit lead over Trump there.

“By any stretch of the GOP imagination, as many as 18 other states that Mitt Romney lost would probably be better targets for Donald Trump than California,” said Neil Newhouse, who was GOP nominee Romney’s pollster in 2012. “Recent polling indicates that it may not be far-fetched for the Trump campaign to believe they can expand the electoral playing field, but overreaching can expend scarce resources and divert them from states that are more realistic targets.”

During a three-day swing through the Golden State last week, Trump repeatedly told supporters he intends to contest the state in the fall. “I’m going to play heavy in California,” Trump said in Redding on Friday. “Right? I think we can win.”

Trump also said he harbors ambitions to wrest Oregon and Washington from Democratic hands. Neither state has gone Republican since Ronald Reagan won them in his 1984 landslide.

“We’re going to play in places where Republicans don’t traditionally play in — that’s in addition to the Floridas of the world,” Trump campaign manager Corey Lewandowski said in a recent interview.

Trump had been scheduled to meet with Florida Gov. Rick Scott on Monday in New York to discuss strategy in the Sunshine State, which is a quadrennial battleground. But Scott decided to postpone the meeting Sunday to stay in Florida and monitor a storm.

There are also concerns about Trump’s continued targeting of fellow Republicans.

During an event in New Mexico last month, he criticized Gov. Susana Martinez — the first Latina governor in the nation — only to reverse course the following week by telling a local newspaper he would like her endorsement. In response, Martinez’s office said she would meet with the mogul.

Trump’s initial criticism of Martinez dominated news coverage, at least partly overshadowing events such as the release of a highly critical analysis of Clinton’s use of email as secretary of state.

“There have been a number of missed opportunities,” said Republican strategist Kevin Madden, who worked for Romney. “They seem to be a product of a campaign that is winging it from day to day.”

Even amid such criticism, some Republicans see upsides for Trump. Cole said that according to polling he has conducted in his congressional district, Trump’s favorability among Republicans is on the rise. Some recent public polling has also showed Clinton and Trump in close competition in key swing states.

Cole also pointed to Trump gaining the endorsement last week of Ryan, the nation’s ­highest-ranking Republican. After refusing to back Trump for weeks, Ryan wrote a guest column for his hometown newspaper Thursday explaining that he would vote for Trump while still voicing disagreements when necessary.

The next day, Ryan followed through — criticizing Trump’s comment about Curiel as “out of left field.”

“He clearly says and does things I don’t agree with, and I’ve had to speak up on time to time when that has occurred, and I’ll continue to do that if it’s necessary,” Ryan told a Wisconsin radio station. “I hope it’s not.”

Trump shows little sign of changing course and continues to champion policies that Ryan and other establishment Republicans oppose. At his Redding rally last week, for example, Trump led one of his regular chants on building a massive wall along the U.S.-Mexico border.

“Build that wall!” Trump said to the cheering crowd.

“The wall got 10 feet higher!” one man yelled out in response.