It wasn’t so long ago that Republicans were congratulating themselves for having put forward the most diverse group of presidential candidates from either political party, ever.

But the message Americans are hearing from the 2016 GOP field is sounding more and more exclusionary. That was evident most recently in a comment from retired neurosurgeon Ben Carson, who is running near the top in national polls, that he “absolutely would not agree” with a Muslim becoming president.

Carson attempted Tuesday to walk back that statement, made over the weekend on NBC’s “Meet the Press” and reiterated in an interview Monday on Fox News. He insisted that he had been referring only to religious radicals and blamed “the P.C. culture” — political correctness — for the controversy that ensued.

Yet inflammatory rhetoric has become routine in the presidential race, where the Republican field is led by the bombastic Donald Trump.

Trump has remained ahead in the polls even as he has issued a stream of offensive comments about women — including popular Fox News host Megyn Kelly and his GOP rival Carly Fiorina — and branded illegal immigrants as rapists and murderers. The real estate mogul also came under fire last week for not challenging a supporter at a rally who told him that “we have a problem in this country: It’s called Muslims.”

Republican presidential candidates are weighing in on controversial comments made about Muslims. Here's what they're saying. (The Washington Post)

But none of that appears to have fazed many conservative Republicans. In fact, a vocal segment of the GOP base applauds what it sees as truth-telling by political outsiders.

“People are fed up,” said Robert Kearns of Springfield, Ohio, who was attending a Carson rally Tuesday at Cedarville University. “Why do you have a Trump emerge? Because he’s someone who is willing to say that we’re not going to stand for this.”

Meanwhile, the more mainstream GOP candidates don’t appear to be gaining much traction. On Monday, Wisconsin Gov. Scott Walker was forced to abandon what once seemed to be a promising bid for the White House.

‘A searing impression’

Ultimately, the party’s message will be shaped by its nominee, and there are still more than four months to go before the first votes are cast in the Iowa caucuses.

However, many Republicans worry that the image of these early months will last. “This year is different, and what is happening now is leaving a searing impression,” said Peter Wehner, who headed the White House Office of Strategic Initiatives under President George W. Bush. “This is toxic for the Republican Party — potentially lethal for it.”

The leading candidates, Wehner added, are “sending a message in bright, Trump-like lights to nonwhite voters that they are not welcome.”

In 2012, the GOP alienated Latino voters when nominee Mitt Romney said he favored “self-deportation,” the idea of making life so difficult for illegal immigrants that they would leave on their own. Romney got 27 percent of the Hispanic vote, a dismal showing compared with the 44 percent Bush received in 2004.

But today, some candidates are talking about far harsher immigration measures. Trump has said he would forcibly deport the estimated 11 million people who are in the country illegally, and a number of GOP contenders have spoken in favor of ending the constitutional provision granting citizenship to anyone who is born in this country.

Some Republicans have lamented much of this year’s inflammatory rhetoric as selective, politically expedient readings of the Constitution.

“We often use the Constitution the way we do the Bible. We treat it like a buffet line. We take what we like, and we leave the rest behind,” said former Oklahoma congressman J.C. Watts, who supports Sen. Rand Paul (Ky.) for the Republican nomination.

Others decry what they say are assaults on religious liberty with respect to those whose beliefs run counter to the Supreme Court’s recent decision legalizing same-sex marriage. Yet some of the same GOP figures would disregard the fact that the Constitution does not allow a religious test of people who run for president.

Carson is among those who have also stirred fears of a secret Muslim agenda to impose sharia law, the Islamic penal code, in this country.

“I wouldn’t expect those remarks would hurt Dr. Carson in Iowa. I think they help him,” said Rep. Steve King (R), a conservative leader in that state. “The people on our side who pay any attention to this at all understand sharia is incompatible with the Constitution and that a sincerely devout Muslim — I might say, a devout Islamist — cannot seriously give an oath to support the Constitution, because it’s incompatible with his faith.”

So potent is the right’s fear of this hypothetical threat that seven Republican-dominated states have banned sharia law or sharia courts that some claim Muslims might convene to contravene state law.

Anger in the base

There is no small paradox at work in the shrillness of the rhetoric. The Republican field is more representative than ever of an increasingly diverse America — and more so than the all-white Democratic field.

Among the 15 Republican candidates are an African American (Carson), a woman (Fiorina), two Cuban Americans (Sens. Marco Rubio of Florida and Ted Cruz of Texas) and an Indian American (Louisiana Gov. Bobby Jindal).

Former Florida governor Jeb Bush is married to a Mexican-born woman and speaks fluent Spanish. And Paul has made a point of appearing before African American groups, criticizing sentencing laws that he says put a disproportionate number of blacks in prison.

But the chief dynamic that has driven the fight for the nomination is a current of anger in the GOP base, aimed at what many see as unsettling cultural and political changes and a party establishment that they believe has failed them.

“Many in the GOP have gotten more and more angry during the Obama years, and the conservative media environment has gotten more shrill and less reasonable,” said Matthew Dowd, a top strategist in Bush’s 2004 reelection campaign. “In addition, conservatives have seen more of their traditional institutions under attack, and their version of America going away.”

That was the view expressed Tuesday by Ruth Hunsberger of Urbana, Ohio, after Carson’s rally in Cedarville: “How could it come to the point that people would turn their backs on Christians? Everything has eroded so badly. And it has just come so quickly.”

After Romney’s loss in 2012, the Republican establishment responded by changing the mechanics of how it picks a nominee, including fewer debates and a more compressed calendar of primaries and caucuses.

But GOP leaders did little to address the rage that was roiling their base and that had fueled the rise of anti-establishment forces such as the tea party movement. Efforts to pass legislation that would signal more inclusiveness, such as an immigration overhaul, foundered in Congress.

“They didn’t deal with the fundamental problem, which was their voters,” Dowd said. “They picked process over people.”

David Weigel contributed to this report.