Just six days after the 9/11 attacks on the World Trade Center and the Pentagon, then-President George W. Bush spoke at the Islamic Center of Washington, D.C., seeking to quell Americans' fears about Muslims and Islam: "The face of terror is not the true faith of Islam. That's not what Islam is all about. Islam is peace. These terrorists don't represent peace. They represent evil and war,” said Bush, striking a tone that he would continue throughout his presidency, even as he ordered invasions of Afghanistan and Iraq.

After that first speech, Bush would repeatedly distinguish the war on terror from a war on all Muslims, saying Islamist terrorists were “traitors to their own faith” -- and that Muslim Americans were loyal citizens who contributed to society, including by serving in the U.S. armed forces.

But if you ask the top presidential candidates in the current-day GOP, Bush might as well have been speaking Arabic. Leading candidates Donald Trump, Ben Carson and Ted Cruz have been fanning the flames of anti-Muslim sentiment throughout the primary season. Most recently, real estate mogul Trump has suggested the need for surveilling and closing down American mosques and the creation of a special ID for Muslim Americans, while retired neorosurgeon Ben Carson likened Syrian refugees to “rabid dogs” and said in September that “he would not put a Muslim in charge of this nation.” Even Jeb Bush has distanced himself from his brother’s unifying message, suggesting that the U.S. should accept Christian but not Muslim Syrian refugees.

This radical shift in tone by leaders of the Republican Party isn’t accidental -- public sentiment toward Muslims has become increasingly negative, especially among GOP voters and especially since the Paris attacks on Nov. 13. Pandering to that feeling has proven a successful strategy for Trump and Carson, who are leading in the polls. Whether marginalizing an entire group based on religion or ethnicity can be successful in a general election remains to be seen, though experts say  it’s unlikely.

“Bush’s response after 9/11 was very measured, and reminded Americans, many of whom weren't familiar with Islam, that the vast majority of Muslims were peaceful,” said Melissa Deckman, a professor of political science at Washington College who focuses on the intersection between religion and politics.

“By contrast, you have this series of candidates who are really pandering to the far right of the Republican base. It’s not hard to figure out why,” Deckman added. “If you look at polling data, Republicans are far more likely to express concerns about terrorism than Democrats, and they’re more likely to believe that Islamic values are at odds with American values.”

It’s true: A survey from the Public Religion Research Institute released in November found that 79 percent of Republicans are concerned about terrorism, up from 57 percent in 2011. And 76 percent of Republicans (77 percent of Tea Party members) agreed that Islam is at odds with American values and way of life, while only 43 percent of Democrats said the same.

“The Republican base has become increasingly suspicious of Muslims,” said Geoffrey Layman, a professor of political science at Notre Dame, who has studied the perception of Muslim Americans in the U.S. “The strongest anti-Muslim sentiment has come from outsider candidates like Trump and Carson, who play on the fear of America not looking like it used to look. They’ve been successfully capitalizing on disenchantment and alienation, especially among working-class, less-well-educated white voters, who are wary of major changes in American society in general.”

It's certainly not the first time in American political history that immigrants or religious groups have been demonized in an effort to gain votes. 

“Throughout U.S. history, we have seen anti-religious rhetoric against various groups used in politics. Anti-Catholicism was a very strong theme much earlier in the 20th century. And whisper campaigns against Jews have sometimes been a factor in electoral politics,” said Marie Griffith, director of the John C. Danforth Center on Religion and Politics at Washington University in St. Louis.

Griffith points to Al Smith, the Democratic nominee for president in 1928 who lost in a landslide to Herbert Hoover, largely as a result of his Catholic faith, which was exploited by the Hoover campaign. By the time John F. Kennedy ran for president in 1960, however, he was able to squelch fears of a Catholic president, addressing the issue head-on in a landmark speech.

The most successful tactics in modern presidential campaigns, however, are the more coded appeals to voters, says Mark Rozell, acting dean and professor at the George Mason University School of Policy, Government and International Affairs. Think “Nixon’s ‘law and order’ rhetoric, or the infamous Willie Horton ads on behalf of George H.W. Bush in 1988. What is different here is the direct targeting by name of a minority group that is fueling strong poll numbers for Trump and Carson, in particular.”

But experts add that in modern national elections, the strategy of targeting a minority group outright can only get candidates so far.

“It is important to be mindful that the nominating process focuses on only a segment of the overall voting population and in a large multi-candidate GOP field, a candidate is able to somewhat stand out by the use of highly divisive appeals that play to public fears,” added Rozell.

In a national election, the electorate widens and is less likely to be swayed.

“These strategies tend to work in the short run, and a little better at local, state and congressional-level elections, where you have a less diverse electorate,” said Layman. “But in the long run, they tend to fail.”