Sen. Strom Thurmond of South Carolina was debating the satirist Harry Golden at Virginia Tech University when a dean interrupted the proceedings with the horrible news that Martin Luther King Jr. had been assassinated. Stunned students groaned in despair, prompting Golden to offer an impromptu tribute, calling April 4, 1968, “a sad day for the world.”

But Thurmond used the occasion to denounce the slain civil rights leader. “I disagree with Mr. Golden’s estimate of Dr. King,” Thurmond said. “He was an agitator, an outside agitator, bent on stirring people up, making everyone dissatisfied.”

It was a bizarre verdict but one not confined to rabid segregationists like Thurmond. University of New Hampshire historian Jason Sokol’s revealing new book, “The Heavens Might Crack,” makes clear that the opinion was shared by millions of white Americans.

It may seem inconceivable now, but only one Southern senator or congressman attended King’s Atlanta funeral: Georgia’s Rep. Fletcher Thompson, a Republican. As President Lyndon Johnson, who by then was not on speaking terms with King, considered going to Atlanta for the service, Tennessee Gov. Buford Ellington said that “the president has done enough for this man. … His going very likely would cause serious white backlash.” In the end, Johnson skipped King’s funeral after attending an earlier memorial service for King at Washington National Cathedral.

Sokol mines oral histories, books and contemporaneous news stories to pull together an account that reminds us that King was a radical who ignited passions both good and bad. The King memorialized on the Mall, and in the many hundreds of schools and streets around the world that bear his name, is far more complicated than the unthreatening leader who sought to have people judged not by the color of their skin but by the content of their character.

King’s dream of racial harmony is just part of his legacy, albeit the part that has allowed him to become one of the most lionized figures in American history. The more controversial aspects of King’s worldview – his opposition to the Vietnam War, his embrace of what Sokol calls democratic socialism, his determination to force the nation to attack poverty, his statement that “a society that has done something special against the Negro for hundreds of years must now do something special for him” and his call for the “reconstruction of the entire society” – made him a lightning rod. King was awarded the 1964 Nobel Peace Prize, but a 1966 poll found that 72 percent of white Americans had an unfavorable view of him.

While those broad outlines of King’s story are well chronicled and fairly well known, the real punch in Sokol’s book comes as it drives home the depth of the animus stirred by King and how it lingered in the months and years after his assassination. Sokol argues that King achieved universal hero status only after his legacy was scrubbed, stretched and softened to the point that it became elastic enough to support both sides of many divisive issues. King has been cited by both opponents and proponents of affirmative action, by supporters and critics of the Black Lives Matter movement, and even by those in opposing camps on the national anthem protests launched by former San Francisco 49ers quarterback Colin Kaepernick. As King’s message has been diluted, his popularity has risen. These days, opinion polls find King to be among the most revered Americans.

Sokol closely examines some of the controversies that arose after King’s death to make plain that King’s current place as an American icon is a far cry from where he stood a half-century ago. In places, the anecdotes that animate “The Heavens Might Crack” feel small-bore, but by its conclusion the book becomes a case study in the curious ways in which history evolves.

In the years before his death, King reached a crossroads in black America. Many young leaders were impatient with his strategy of nonviolent protest and his continued push for integration, and some observers saw him as a leader with a diminishing following. “The verdict was that Martin was finished,” wrote David Levering Lewis, one of King’s early biographers.

But King’s death changed that. No doubt, his assassination triggered an outpouring of grief, and untold millions were inspired by his leadership. But at the same time, King’s murder sparked anger in many parts of black America while unleashing an undercurrent of hateful bile from some whites.

As word of King’s assassination spread, black students and their sympathizers protested on college campuses, and riots broke out in hundreds of cities across the country. Sokol argues that the assassination added fuel to the Black Power movement because for many black Americans, King’s death revealed the irrational hate that even an avowed man of peace could unleash.

Sokol finds disturbing letters to the editor and commentary that showed the depth of anger many whites felt toward King, even in the immediate aftermath of his death. Some of the commentary was as unhinged as anything found today on social media. More than one letter writer thought King had it coming. He “reaped exactly what he sowed,” wrote one. “He taught people to disobey laws, and his assassin simply disobeyed the law against murder.”

Others could not understand the official tributes to King. “The leaders of the government pay homage to a rabble rousing, riotous insurgent,” one reader wrote to the Tennessean newspaper in Nashville. “I am sick to my soul.”

It would take decades for King’s legacy to become the hollowed one we all know now. For a long time, even the simplest, most symbolic gestures to commemorate King could be fraught. Sokol traces some of the surprisingly pitched battles to rename streets in King’s honor.

In Austin, white residents opposed renaming 19th Street after the slain leader. “We, the property owners, own 19th Street,” one opponent said. People circulated petitions and filed a lawsuit, but finally the street was renamed for King. People in San Diego waged a similar battle over Market Street, which runs through that city’s downtown. The street was renamed for King in the late 1980s but later reverted to Market Street after nearly 80,000 petitioners put the issue on the ballot, where it won close to 60 percent of the vote.

The fight to establish a national holiday in honor of King was similarly difficult. Then-Rep. John Conyers (D-Mich.) offered a bill to make King’s birthday a national holiday just days after the assassination. But the first King national holiday would not be celebrated until 18 years later, as many in Congress opposed it for stated reasons ranging from the cost of a holiday to suggestions that King had consorted with communists.

Even when the bill passed in 1983 (its implementation was delayed until 1986), thousands of letter writers urged President Ronald Reagan to veto it. One cited by Sokol called King a man “of immoral character whose frequent association with leading agents of communism is well established.” Days later, Reagan replied, “I have the same reservations you have.” He signed the legislation anyway, but not before observing that the growing veneration of King was “based on image not reality.”

After reading Sokol’s book, it is clear that Reagan’s assessment was correct – but not in the way he intended.

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