AS a Briton who, like millions of my compatriots, opposed the American-led invasion of Iraq in 2003, I did not expect to ever find much to admire about President George W. Bush. But as a Muslim who has come to work in America, I have recently had to revise my opinion.

Less than a week after the Sept. 11, 2001, attacks that killed 2,996 people, President Bush held a news conference at the Islamic Center of Washington. “The face of terror is not the true faith of Islam,” he said, flanked by imams and community leaders. “Islam is peace.”

It was a message repeated often in the months and years afterward. “Our war is against evil,” the president said, “not against Islam.”

Fourteen years later, such remarks seem distant, if not improbable, amid the miasma of anti-Muslim hate and fearmongering fostered by the Republican candidates for president.

In recent days, Donald J. Trump has claimed that “thousands and thousands” of Muslims in Jersey City celebrated the fall of the Twin Towers — a statement refuted by the city’s mayor and rated by the fact-checking watchdog PolitiFact as “Pants on Fire.” Mr. Trump has also said he “would certainly implement” a federal database to register America’s estimated three million-plus Muslims and would not rule out asking Muslim-Americans to carry a special form of IDnoting their faith.

Another contender, the former neurosurgeon Ben Carson, said that he is opposed to a Muslim’s being allowed to run for president because Islam is “inconsistent” with the Constitution. He also compared some Syrian refugees to “rabid dogs.”

The anti-Muslim animus extends even to establishment Republican candidates. Jeb Bush, the former Florida governor, said he wouldprefer to give asylum to Christian, rather than Muslim, refugees. Senator Marco Rubio of Florida, meanwhile,tried to outdo Mr. Trump by saying he’d close not only mosques, but Muslim cafes and diners, too.

Senator Rand Paul, the libertarian who earlier this year held up the renewal of the Patriot Act with a filibuster-like 11-hour speech in the Senate, now demands “heightened scrutiny” of Muslim immigrants. His Senate colleague Ted Cruz claims that Shariah law “is an enormous problem” in the United States.

Working our way down the roster, what of the former governor of Arkansas Mike Huckabee or Gov. John Kasich of Ohio? Mr. Huckabee has called Islam “a religion that promotes the most murderous mayhem on the planet,” and Mr. Kasich has proposed a federal agency to spread “Judeo-Christian Western values.”

Gov. Chris Christie of New Jersey is an exception among Republican presidential candidates for pushing back against the anti-Muslim“crazies” and their “crap” about Shariah law. That was in 2011, but now even Mr. Christie has taken a hard-line stance against Syrian refugees. That Mr. Christie is polling at about 3 percent, while Mr. Trump leads the field, suggests that Islamophobia is a vote winner with the modern G.O.P.

According to an ABC News/Washington Post poll, unfavorable views of Islam jumped 18 points among Republicans between October 2001 and March 2009. The election of a nonwhite president with Hussein as a middle name, not to mention the rise of the self-declared Islamic State, only served to harden the prejudices of some core G.O.P. voters.

Today, fully 83 percent of Republicans agree with Dr. Carson that a Muslim shouldn’t be president. Only half (49 percent) of G.O.P. voters in Iowa think Islam should be legal in the United States.

It is important to recognize how out of sync such views are with the Republican Party’s historical record. In 1957, Dwight D. Eisenhower became the first sitting president to speak at an American mosque. At the inauguration ceremony of the same Islamic center that Mr. Bush visited in 2001, Ike assured his audience that the nation “would fight with her whole strength” for Muslims’ right to worship according to their conscience.

In 1974, Gerald R. Ford became the first president to send an official message to Muslim-Americans for Eid al-Fitr, the festival that marks the end of the holy month of Ramadan, saying that America’s diversity had been “greatly enhanced” by the “religious heritage” of Muslim-Americans. In 1981, Ronald Reagan nominated America’s first Muslim ambassador, the convert Robert Dickson Crane.

These were the Republican footsteps that Mr. Bush was following in 2002 when he became the first president to visit an American mosque on Eid. He had the advantage, of course, of being an incumbent president, rather than a prospective candidate. Yet he and advisers like Karl Rove and Michael Gerson understood that demonizing Muslims and depicting Islam as “the enemy” not only fueled Al Qaeda’s narrative but also hurt their party’s electoral prospects.

Minorities matter — in general, if not primary, elections. A studycommissioned by the Republican National Committee in the wake of Mitt Romney’s 2012 defeat noted how “many minorities wrongly think that Republicans do not like them or want them in the country.” To be sure, Muslims constitute just 1 to 2 percent of voters in the United States, but in 2000, when the presidential election turned on just 537 votes in Florida, more than 46,000 Muslims in that state voted Republican. In the view of the influential conservative activist Grover Norquist, “George W. Bush was elected president of the United States of America because of the Muslim vote.”

Mr. Bush’s foreign policy may have harmed Muslims abroad, but at home he courted Muslim-American voters and refused to lazily conflate Islam with terrorism. Mourning Mr. Bush’s re-election in 2004, the economist John Kenneth Galbraith remarked: “I never thought I would ever long for Ronald Reagan.” I recognize the sentiment, as I listen to the irresponsible Muslim-hating rhetoric of the current crop of candidates.

I never thought I’d say it, but now I long for the Republican Party of George W. Bush.