Many prominent conservatives have, to their credit, responded to Donald Trump’s call to ban Muslims from entering the United States with horror. “It is un-Republican. It is unconstitutional. And it is un-American,” declared the head of the New Hampshire Republican Party. The head of the South Carolina GOP said it “send[s] a shiver down my spine.” Even Dick Cheney said it “goes against everything we stand for and believe in.”

The problem is that Trump didn’t invent this. He’s exploiting a market for anti-Muslim bigotry that conservatives have nurtured for more than a decade. I don’t doubt that many on the right are genuinely outraged by Trump’s comments. But he’s just the latest, and most successful, in a string of GOP contenders—from Herman Cain in 2012 to Ben Carson this year—who have proposed denying American Muslims basic rights. If conservatives want to stop not only Trump but the Trumps who will follow, they have to establish the same red lines for anti-Muslim bigotry they’ve established for anti-Semitism. I have a suggestion for where to start.

Three days after September 11, Ann Coulter proposed that America “invade their [Muslim] countries, kill their leaders, and convert them to Christianity.” A week later, she mused that, “Congress could pass a law tomorrow requiring that all aliens from Arabic countries leave.” To its credit, National Review, which had published Coulter’s column, said it would no longer do so.

But Coulter kept appearing on TV. And she remained just as bigoted as ever. Asked in 2003, whether airlines should offer “Muslim-free air travel?” Coulter responded that, “I’m way ahead of you. I think airlines ought to start advertising: ‘We have the most civil-rights lawsuits brought against us by Arabs.’’’ Asked how Muslims would then travel, she responded: “They could use flying carpets.” When a student from the University of Western Ontario told Coulter in 2010 that she didn’t own a magic carpet, Coulter replied: “Use your camel.”

It gets worse. In 2006, Coulter said, “our motto should be post-9/11, ‘raghead talks tough, raghead faces consequences.’” On another occasion she said, “our motto should be after 9/11: Jihad monkey talks tough; jihad monkey takes the consequences. Sorry, I realize that’s offensive. How about ‘camel jockey’?”

Coulter is not a marginal figure. Since 9/11, according to the liberal group Media Matters, she’s appeared at least 192 times on CNN and MSNBC and a whopping 450 times on Fox. In that time, according to BookScan, she’s sold 2.3 million books, more than four times many as David Brooks. A few years ago, a sympathetic profiler called her “the Rush Limbaugh of the printed word ... the most successful conservative writer working today ... No 21st century conservative writer—male or female—comes even close.”

In her exploitation of bigotry, Coulter is not only one of Trump’s forerunners, she is one of his inspirations. Trump has called Coulter’s latest book, Adios, America! The Left’s Plan to Turn Our Country into a Third World Hellhole, a “great read.” She’s warmed up for him at rallies. And she’s claimed credit for some of Trump’s most notorious lines. “Where do you think all that spicy stuff about Mexican rape culture came from?” she tweeted this summer. “@realDonaldTrump got an advance copy.” Coulter has been ahead of Trump on Muslims, too. This January, after the attacks on Charlie Hebdo in Paris, she suggested that “maybe you take a little pause in Muslim immigration for a while.”

Like Trump, Coulter gets away with it, in part, because she’s considered an entertainer: “Bold, brash, provocative, talented, fearless, witty, and outrageous,” in National Review’s words. But her massive success—fueled by massive media exposure—has shown other conservatives that bigotry sells. Mike Huckabee has gotten into the Islamophobia game in recent as years as well. In 2011, he said Christians shouldn’t rent space in their churches to Muslims because “Muslim group[s]” say “that Jesus Christ and all the people that follow him are a bunch of infidels who should be essentially obliterated.” In 2013, he called Islam “a religion that promotes the most murderous mayhem on the planet in their so-called holiest days ... Muslims will go to the mosque, and they will have their day of prayer, and they come out of there like uncorked animals—throwing rocks and burning cars.” In the years Huckabee made those comments, he hosted his own Fox show.

All this helps explain why Republicans, who disproportionately watch Fox and read Coulter, are so much more hostile to Muslims and Islam than Democrats. Last month, according to a survey by the Public Religion Research Institute, 43 percent of Democrats said Islam was incompatible with American culture, which is bad enough. But among Republicans, it was 76 percent. A September Public Policy Polling survey found that only 49 percent of Iowa Republicans believed Islam should be legal in the United States. (The rest thought it should be illegal or weren’t sure. The survey didn’t ask Democrats.)  Among Trump supporters, the figure was 38 percent. Among Huckabee supporters, it was 28 percent.

When it comes to violent jihadism, conservatives are quick to say that it’s not enough to go after leaders. You must confront the culture from which they arise. It’s time they took their own advice. If the right wants to defeat Trump, and the Trumps who will almost certainly follow, it needs to draw a clear line between being a conservative and being a bigot, as William F. Buckley did decades ago when he expelled anti-Semites from his movement’s ranks. When Ann Coulter stops appearing on Fox, we’ll know that the right’s intellectual counterattack against Trumpism has truly begun.