In a speech in Reno on Thursday, Hillary Clinton called out some of the weirder and darker corners of the Internet in an effort to reinforce Donald Trump's associations with the racist fringe of American conservatism.

"This is someone who retweets white supremacists online, like the user who goes by the name 'WhiteGenocideTM,' " Clinton said. "Trump took this fringe bigot with a few dozen followers and spread his message to 11 million people."

The combination of social-media jargon and extreme-right lingo might have made Clinton's remarks seem like a new and different kind of speech for a major party's presidential nominee.

Yet progressive politicians — including Clinton's husband — have been delivering similar speeches for decades. Sometimes, conservative politicians' messages can seem to exploit voters' racial anxieties. Progressive candidates often respond by emphasizing the racial dimension of those messages and turning their opponents' rhetoric against them.

Political scientists have suggested a couple of ways the strategy might work to persuade voters. Most obviously, progressive candidates might be able to win over conservative voters who also support racial equality by convincing them that the conservative candidate is exploiting bigotry.

Less intuitively, this strategy might also succeed with white Americans who do harbor biases against people of color if those biases are unconscious. On a rational level, according to this reasoning, most white Americans are genuinely committed to a colorblind ideal of racial equality. As political scientist Tali Mendelberg of Princeton University has argued, white voters may be unconsciously persuaded by racial appeals but will reject those appeals once the bigotry is pointed out to them.

"Most people want to avoid not only the public perception that they are racist, but also thinking of themselves as racist," Mendelberg has written. "White voters respond to implicitly racial messages because they do not recognize these messages as racial and do not believe that their favorable response is motivated by racism."

Republican leaders have rejected the notion that their appeals to voters operate through unconscious prejudice.

When former vice president Richard B. Cheney was asked last year whether criticism of President Obama and former Attorney General Eric Holder was racially motivated, he accused Democrats of "playing the race card."

"This party does not prey on people's prejudices," Rep. Paul D. Ryan (R-Wis.) said earlier this year. "We appeal to their highest ideals. This is the party of Lincoln." The speaker of the House is now supporting Trump.

'Race against race'

Mendelberg studied the presidential campaign of 1988, in which Democratic candidate Michael Dukakis confronted a notorious advertisement attacking his record on crime. The spot featured an image of a black man and convicted murderer named Willie Horton, but did not discuss race explicitly.

This ad, titled "Weekend Passes", was created by the National Security PAC in 1988. (National Security PAC)

Mendelberg found that initially, the advertisement nudged racially conservative white Americans to support George H.W. Bush, who was then vice president. Yet when Democrats started to describe the advertisement as a covert appeal to racial anxieties about black crime in the final weeks of the campaign, the advertisement seemed to lose its persuasive effect, according to Mendelberg's surveys.

Mendelberg also cites several other examples of progressive politicians using this same strategy of turning a covert racial appeal against a conservative opponent.

Southern Democrats have been using the strategy at least since 1951. "For 20 years, my opponent has known nothing to run on but prejudice, hate, fear and the Negro question," Paul Johnson, a Mississippi Democrat, declared during his unsuccessful gubernatorial campaign that year. 

In 1964, President Lyndon B. Johnson ran a television advertisement against Barry Goldwater, the Republican nominee who opposed civil rights legislation, with images of hooded Klansmen and a burning cross. An actor quoted a leader in the Klan endorsing Goldwater.

A 1964 campaign ad for Lyndon B. Johnson for president of the United States. (The LBJ Library)

Later, during John West's campaign for governor of South Carolina in 1970, he used a similar strategy when his opponent called for "discipline" in schools and ran television spots that mentioned the riots in the Watts neighborhood of Los Angeles several years earlier.

"I will not by word or deed or action do anything to inflame or polarize class against class, rich against poor, color against color," West said. He won the race.

Bill Clinton echoed West's language in announcing his presidential campaign in 1991. "For 12 years, Republicans have tried to divide us — race against race — so we get mad at each other and not at them," the future president said.

"Clinton understood that his party was vulnerable to racial appeals, and he had a long southern tradition of combating racial appeals on which to draw," Mendelberg wrote.

A shift in strategy

The strategic landscape of the current presidential campaign has shifted abruptly in the past week, as both candidates are now focused on Trump's association with prejudice. Trump was one of the most vocal proponents of the theory that Obama was born outside the United States, and he announced his campaign by labeling Mexicans "rapists."

Now, Trump is seeking to avoid an explicit association with the far right by moderating his position on immigration. And Clinton is trying to force voters to keep that association in the front of their minds.

In her speech in Reno, she connected Trump with the "alt-right," an informal, far-right movement focused on white identity whose members share their views in online forums. Her campaign also produced an advertisement featuring members of the Klan endorsing Trump, a spot that could almost be an extended version of the one Johnson aired in 1964.

An ad released by the Hillary Clinton campaign says white supremacist and alt right leaders support Donald Trump for president. (Hillary Clinton)

Yet although the candidates have begun campaigning as though the year is 1988 or 1964, they are doing so in a political environment that may have fundamentally shifted since then, said Nicholas Valentino, a political scientist at the University of Michigan.

Many of Trump's supporters might no longer be put off by explicit discussions of race. The candidate himself has argued that political correctness is outdated and dangerous. Indeed, Valentino suggested, Clinton's principled dismissal of their views on race might even be extra motivation for them to vote for Trump.

Valentino and his colleagues recently conducted experiments in which they found that racially conservative participants were no more receptive to political messages that discussed race subtly and implicitly than to those that discussed race explicitly. Voters, the researchers concluded, are now willing to listen to explicit discussions of race.

The research doesn't imply that the campaigns' new strategy will be irrelevant to voters, Valentino said. As Clinton charges Trump with racism and Trump responds, the two candidates have a chance to compete for moderate and conservative white voters who are put off by prejudice. Valentino's research suggests this group is largely women.

These voters might have always found Trump's rhetoric unappealing, consciously and otherwise. All the same, they might be persuaded to support him because they dislike Clinton or her policies, Valentino suggested. He said that Trump is trying to win them by shifting his position on immigration and by appearing concerned about the problems of black communities.

"When he moves away from this explicit kind of rhetoric in the most recent days, and he’s starting to soften his position on immigration, for example, that’s an appeal to white moderates and, in particular, women," Valentino said. "That’s not a message to African American voters."