Editor’s Note: Julian Zelizer is a professor of history and public affairs at Princeton University and author, with Kevin Kruse, of the new book “Fault Lines: A History of the United States Since 1974.” Follow him on Twitter at @julianzelizer. The opinions expressed in this commentary are his own. View more opinion at CNN.

CNN  — 

The media have spent several days covering the noxious chant – “Send them back” – that broke out at President Donald Trump’s North Carolina rally. The chant was inspired by a tweet from the President, saying that congresswomen Ilhan Omar, Alexandria Ocasio-Cortez, Ayanna Pressley and Rahida Tlaib should “go back” to the “broken and crime infested places from which they came.”

Critics rightly condemned the President for encouraging this racist message among his loyal base. No longer shy about calling out Trump’s use of racist tropes, politicians and reporters came down hard on his injection of dangerous rhetoric into his reelection campaign. And though Trump later said he didn’t like the chant, he did nothing to stop it.

But here’s the problem: This kind of nonstop coverage is exactly what the President counts on. Since Trump declared his candidacy, so many reporters have endeavored to call out the President when he lies or distorts the facts. And though they’ve been more discerning in trying to sift the serious stories from the daily chaos, they still have not figured out how to handle the ways he manipulates the 24-hour news cycle to promote political messages meant to provoke and incite.

Regardless of how news stories evaluate what the President or his supporters have said, the message itself keeps circulating in the public square. From his tweet to the subsequent chants to the endless coverage about the rally, voters in Trump country are hearing “send them back” over and over again, wording with a long history in racist and nativist discourse and one now targeting four prominent women of color. Although analysts are disputing what impact his white nationalism will have in the election, writers like Nate Cohn and David Wasserman have argued that these messages might strengthen the advantages that he has in the Electoral College.

Ever since the start of the television age, politicians have understood that the news coverage of controversial messages can do more than anything to advance a single cause.

In 1964, President Lyndon Johnson’s campaign team released a television spot suggesting that his opponent, Republican Sen. Barry Goldwater, would trigger a nuclear war. The “Daisy” ad depicted a young girl counting the petals on a flower before viewers heard a government voice counting down in more ominous fashion. The ad concludes with the image of a nuclear mushroom cloud.

Republicans were furious. Illinois Senator Everett Dirksen, a Republican who was pivotal to helping Johnson pass the Civil Rights Act of 1964, denounced the ad for taking “political advertising to a depth never approached in the history of television.”

The Johnson team pulled the ad, but the mission was complete. And, according to political journalist Theodore White, “the shriek of Republican indignation fastened the bomb message on [Goldwater’s campaign] more tightly than any calculation could have expected.” The news coverage of the ad further promoted the message that Johnson’s team wanted to promote: Goldwater could not be trusted with the nation’s political arsenal.

This tactic has been used many times since, by candidates as well as interest groups. During the debate over President Bill Clinton’s health care plan in 1993 and 1994, the Health Insurance Industry of America released a blistering ad that featured a white suburban couple, Harry and Louise, worrying about what the plan would do to their health care coverage. Louise, looking at a copy of the proposal, tells her husband that “this plan forces us to buy our insurance through these new mandatory government health alliances.” Sharing the concern, Harry adds that it would be “run by tens of thousands of new bureaucrats.”

The ad ran in only a handful of major markets. But the small insurance lobby understood how “Daisy” had worked. The media coverage of the ad spread the message to even larger markets and made it a national story. Chip Kahn, one of the masterminds of the ads, loved when Clinton attacked them. “Every time we did a new ad … we were on the evening news,” he recalled.

Trump similarly relies on this dynamic. However, unlike in 1964 and even 1994, he can now depend on two additional factors. The first is his Twitter feed, which enables him to get his message to millions of people in a matter of seconds. The second is a 24-hour political news platform, which often will endlessly cover any message he tweets into the universe. The combination of cable news, online publications and his incredibly powerful Twitter feed means that any statement he makes will be subject to ongoing discussion for many days to come. And the more controversial, the greater the coverage.

Follow CNN Opinion

  • Join us on Twitter and Facebook

    The President’s mastery of the modern media environment should not be underestimated. As the campaign season gets underway, editors, reporters and producers will have to decide how much of their resources they allocate to covering, discussing and analyzing Trump’s latest incendiary message.

    His opponents will also have to be more discerning about responding and reacting so much, concentrating instead on building their own agendas and promoting their own issues. The best way to drown out messages – such as the one we saw this past week – is to avoid giving the message more air time than it deserves. And while it’s important to call out racism, it’s equally vital to cover the many policies this administration is proposing and implementing on a day-to-day basis.