On Monday afternoon, South Carolina Gov. Nikki Haley (R) announced that she now supports removing the Confederate flag from the grounds of the statehouse in Columbia. While the reaction of the Republican presidential candidates to the terrorist attack last week in Charleston and the subsequent debate about the flag has been cowardly at best, this is nevertheless a significant moment, with broad implications for the place of race in American politics. To put it simply, the GOP's "Southern Strategy" is all but dead.

As political strategies go, it had a good run — nearly half a century. In 1968, Richard Nixon campaigned on behalf of the "silent majority" who wanted nothing of civil rights protests and uppity young people; he told them he'd deliver the "law and order" they craved, and there was little question who they were afraid of. It was called the Southern Strategy because while the South had been firmly Democratic since the Civil War, Lyndon Johnson's signing of the Civil Rights Act and Voting Rights Act initiated an exodus of Southern whites to the Republican Party, enabling them to build an electoral college majority with the South as its foundation. They would win five of the next six presidential elections with that strategy.

A key component was to make the GOP the default party of white people, by running against what they associated with black people — not just civil rights, but things like poverty programs and crime. It required ongoing reminders of who was on who's side. So in 1980, Ronald Reagan announced his campaign for president in the town of Philadelphia, Mississippi, where civil rights workers James Chaney, Michael Schwerner, and Andrew Goodman were murdered in 1964. He was not there to promote racial healing. Four years earlier, Reagan had told audiences how appalled he was at the idea of a "strapping young buck" buying T-bone steaks with food stamps, and he spent a good deal of the 1980 campaign railing against welfare queens. The race of the (largely fictional) offenders was lost on no one.

And as Stanley Greenberg, then a political scientist and now a leading Democratic pollster, found in his classic 1985 study of Macomb County, Michigan, the entire phenomenon of "Reagan Democrats" was built on racial resentment. "These white Democratic defectors express a profound distaste for blacks, a sentiment that pervades almost everything they think about government and politics," he wrote. "Blacks constitute the explanation for their vulnerability and for almost everything that has gone wrong in their lives; not being black is what constitutes being middle class; not living with blacks is what makes a neighborhood a decent place to live."

So when Reagan's vice president ran to succeed him, it was little surprise that he would employ an inflammatory racial attack against his opponent, repeating over and over again the story of escaped convict Willie Horton. If Michael Dukakis were elected, George Bush's campaign convinced people, hordes of menacing black felons would rampage through the land, raping white women and emasculating their husbands. They didn't say it in quite those words, but they didn't have to; Horton's mug shot (aired endlessly on the news) and the story of his crimes was more than enough. While Bush is now treated as a noble and kind elder statesman, we shouldn't forget that he ran one of the most racist presidential campaigns of modern times. "By the time we're finished," Bush's strategist Lee Atwater said, "they're going to wonder whether Willie Horton is Dukakis' running mate."

Today a Republican presidential candidate wouldn't feature Willie Horton as prominently as Bush did, but it isn't because they've seen the moral error of their ways. It's because it doesn't work anymore. While nearly nine in 10 voters in 1980 were white, their proportion has been dropping for decades, and it will probably be around seven in 10 in next year's election. Mitt Romney won all the Deep South in 2012, and won white voters by more than 20 points — but still lost to Barack Obama by 126 electoral votes.

That doesn't mean the GOP's center of gravity doesn't still lie beneath the Mason-Dixon line. Republicans control nearly all the state governments in the South, which provides them laboratories for their latest innovations in governing, and their hold on the House of Representatives is built on their strength in the South. But as a strategy to win the White House, counting on white people — and the white people who respond when their racial hot buttons are pushed — won't ever succeed again.

The party's candidates are still coming to grips with this reality. They've pandered to racists for so long that not upsetting them is still their default setting; when the issue of the Confederate flag came up, the first response almost all of presidential candidates had was just to say that the people of South Carolina will decide, which is procedurally accurate and substantively irrelevant. But if South Carolina's governor can come out against the flag, it really is a signal that times have changed.

Smart people in the GOP know that if the party is going to win the White House again, they can't do it with the Southern Strategy that served them so well for so long. The question now is whether they can come up with an alternative.