This ad, titled "Weekend Passes", was created by the National Security PAC in 1988. While the advertisement likely had little effect on the outcome of the election, its racial content -- never stated explicitly -- made it one of the most influential in contemporary U.S. politics. (National Security PAC)

One of the most infamous and influential campaign ads in contemporary U.S. politics was “Weekend Passes,” a TV spot about convicted murderer Willie Horton aired by a political action committee against Democratic presidential nominee Michael Dukakis in 1988. The ad attacked Dukakis's record on crime with an image of Horton, who is black — an unstated appeal to racial anxiety.

For all its notoriety, the Willie Horton ad probably had little to do with Dukakis's defeat, the political scientist Tali Mendelberg found. Her surveys showed that the Willie Horton advertisement did seem to increase support for George H.W. Bush among racially conservative white Americans initially, but by the election eight weeks later, the spot had no measurable effect in the surveys.

Mendelberg argues that all it took for Democrats to undercut the advertisement's appeal was to point out its racial connotations, as the Rev. Jesse Jackson did a couple of weeks before the election. She believes Jackson's comment revealed that the Willie Horton spot violated an unwritten rule: Race was taboo. Even those white voters with unfavorable views of African Americans became uncomfortable with the advertisement.

There is no such unwritten rule today, if there ever was. A series of recent surveys suggests that racially conservative Americans are open to explicit conversations about race. The data implies that politicians who use explicit, even inflammatory, racial rhetoric will not pay the kind of penalty at the polls that many observers might expect.

Dog whistles

Back in 1988, Mendelberg reasoned, politicians felt they had to at least appear committed to a kind of colorblind ideal of racial equality. As a result, they avoided talking about race altogether most of the time. If politicians did invoke racial stereotypes, they did so carefully, in code. Mendelberg wrote that voters also wanted equality — at least in principle, whatever their real feelings about race.

“The racial message was communicated most effectively when no one noticed its racial meaning,” wrote Mendelberg, of Princeton University, in 2001. “When people finally noticed, the racial message lost much of its power.”

Mendelberg's argument is still controversial. Many scholars dispute the idea that voters and politicians shared a commitment to a broad principle of racial neutrality.

Nicholas Valentino, a political scientist at the University of Michigan who conducted the recent surveys with his colleagues, finds Mendelberg's arguments about what is often called “dog-whistle politics” persuasive. From his perspective, his new surveys show an important shift in how Americans talk about race.

“Now these issues can be discussed openly,” Valentino said. “There’s nothing unacceptable about that anymore — to talk about race in an explicit way.”

Coded language

This is exemplified in the broad support among Republicans for Donald Trump, who has made more explicit appeals to racial anxiety a crucial part of his campaign.

“When Mexico sends its people, they’re not sending their best,” Trump said in the speech that launched his campaign. “They’re bringing drugs. They’re bringing crime. They’re rapists. And some, I assume, are good people.”

In 1988, the analogue of this comment would have been an advertisement that featured an image of a Mexican immigrant who had committed a crime but that did not mention Mexican  immigrants as a group.

Because racial biases remain widespread, the fact that Americans are comfortable with talking about race also means that inflammatory rhetoric has become more common in public discourse.

Trump and other Republican politicians have themselves argued that in talking about race, too much is treated as out of bounds. In polls, Republicans consistently give Trump high marks for “telling it like it is,” suggesting that some appreciate how freely he gives voice to their racial concerns.

“Political correctness is killing us,” Trump told NBC's “Today” show in February.

Valentino's research, conducted with students Fabian Neuner and Matthew Vandenbroek, suggests Trump is benefiting from a trend that began several years ago.

The presumptive Republican nominee was merely “one of the first to identify those changes and capitalize on them,” Valentino said. “The rules were changed before he got on the scene.”

The researchers conducted the surveys online between 2010 and 2012, using multiple sampling techniques to ensure they had a representative group of Americans. They are in the process of publishing their results.

In each survey, the researchers gauged participants' racial attitudes by asking them whether they agreed with a series of statements such as, “If blacks would only try harder, they could be just as well off as whites."

Respondents also read what was supposedly a news story about the controversy over the Affordable Care Act, President Obama's health-care reform, randomly receiving one of two different versions of the article.

In one version, the controversy was described as explicitly racial. Obama's legislation was described as being more popular with “blacks” and less popular with “whites,” for example. An opponent at a protest was quoted as using a racial slur, while a fictional tea-party lawmaker who voted against the law was quoted as comparing it to "reparations for slavery.”

In the other version, coded language replaced these explicit phrases. Instead of “blacks” and “whites,” the article described tensions “between city and suburb.” Instead of a racial slur, the opponent complained about “bums” and “freeloaders.” For comparison, a third group of participants randomly received a neutral article about the upcoming Winter Olympics in 2014.

Regardless of how conservative they were on race, participants were more likely to tell surveyors that the first version of the article was racially insensitive. That fact, however, did not seem to bother those who had more conservative responses to the questions about racial attitudes. When asked about the Affordable Care Act, they were no more likely than racially conservative participants who had read the coded article to say they supported the policy.

Given the context of politics today, that might not seem surprising. Yet if the participants were uncomfortable with the baldly racial language in the article — as viewers of the Willie Horton ad in 1988 might have been — they would have rejected the critique of the Affordable Care Act as politically incorrect. They would have been less likely to oppose the law than the other group of participants.

Lip service

In a few ways, Trump still follows the old egalitarian racial ideal, noted Ian Haney-López, a legal scholar at the University of California, Berkeley.

For one thing, the New York businessman frames his comments in terms of national origin or religion rather than race or ethnicity. “Trump needs to continue to speak in code," Haney-López said.

Still, Trump can speak more directly than politicians could before. He can explicitly generalize about minority groups — the kind of discussion that many political scientists believe was just unacceptable until recently.

“Ten, 20 years ago, people felt like there was something immoral, unjust, unacceptable about expressly mentioning race, and that’s shifting," Haney-López said.

It is also important to note that Valentino's study focuses on reactions among people who have racially conservative views, not the electorate as a whole. Trump's rhetoric hasn't prevented him from winning the GOP nomination, but it might alienate enough voters to put a victory in November out of reach.

“For national politics, I think it’s a big loser,” said Michael Tesler, a political scientist at the University of California, Irvine.

Breaking the taboo

If the recent surveys do reflect a shift in the politics of race, then it isn't clear what caused the change.

Valentino points to a decline in civility in U.S. politics, a trend that began decades ago as the two major parties began to see each other as enemies rather than as friendly rivals. Perhaps back when politicians from different parties worked together more frequently on major legislation, they had to be careful not to alienate each other with incendiary language about race.

Valentino also speculates that Obama's presidency might be part of the explanation.

The election of a black man to the White House for the first time in history forced politicians and the media to talk about race and racism, breaking the taboo that seemed to exist before. “There’s been a change from the top down in the norms of acceptable political discussion,” Valentino said.

The new public conversation about race inevitably featured a range of views. When they heard public figures articulating feelings they shared, perhaps some racially conservative Americans abandoned the old rules themselves.

“It’s a legitimate discussion,” Valentino added. “It’s a legitimate topic, and therefore whatever your position is on it, your position is legitimized.”