William F. Buckley Jr., left, with Gore Vidal in their 1968 summer showdown on ABC. (Photo courtesy Magnolia Pictures)

According to “Best of Enemies,” the excellent new documentary by Morgan Neville and Robert Gordon, television news coverage changed forever on the night of Aug. 28, 1968.

During a live television debate on ABC News, conservative icon William F. Buckley Jr. called liberal author Gore Vidal “a queer.”

Gordon explains, “A word like that was way across the line. It was so shocking that ABC pulled the broadcast from the West Coast. The task of this film, which opens on Friday, Aug. 7 at Landmark E Street and Bethesda Row Cinemas, was to put that moment in context.”

In the summer of 1968, there were only three major broadcast television networks. ABC was dead last in the ratings war with CBS and NBC. Executives at ABC News decided to take a desperate gamble. They replaced part of the traditional gavel-to-gavel coverage of the Republican and Democratic presidential nominating conventions with a series of live debates. They went all in by choosing two towering public intellectuals who were both ideological opposites and personal enemies.

On the right was Buckley, editor of the influential “National Review” and host of the popular television show “Firing Line.” A conservative Catholic, Buckley was instrumental in reshaping the Republican Party, ultimately helping to usher in the Reagan Revolution. As Gordon notes, “Buckley tried to make the party more reasonable and respectable.”

On the left was Gore Vidal, a prolific author and an estranged member of the Kennedy clan. Vidal’s groundbreaking 1948 novel “The City and the Pillar” dealt with male homosexuality in a forthright and positive manner and his satirical 1968 novel “Myra Breckinridge” skewered gender norms and conventional sexual practices.

Over the course of 10 nights, the two men sparred under the gentle watch of bemused anchorman Howard K. Smith. The debates were an amazing blend of erudite political commentary and barbed personal invective. This impassioned rhetoric was fueled by a fascinating undercurrent of gay baiting.

On the night of Aug. 28, Vidal upped the ante by calling Buckley a “crypto-Nazi.” Gordon notes that Vidal really hit Buckley “where it hurt. Buckley had gone to great lengths to rid the party of that rhetoric. Gore was trying to undermine all of Buckley’s work.”

Buckley lashed out at Vidal’s insult. Rising from his seat, he shouted, “Now listen, you queer, stop calling me a crypto-Nazi or I’ll sock you in your goddamn face and you’ll stay plastered.”

According to the filmmakers, that moment changed the lives of both men and the nature of political discourse in America. Neville says, “It got a lot of attention. People talked about it for years and they were asked about it for the rest of their lives. For Buckley, it was probably the moment he was most ashamed of. He had prided himself on a lifetime of creating difficult situations and maintaining his cool in them. His outburst meant he lost the debate. It certainly haunted him thereafter.”

The impact for ABC was much more positive. The debates were a hit. Before the broadcasts, Neville notes, “CBS and NBC each had around 300 affiliates and ABC only had 150. After the debates, ABC quickly caught up with its rivals and became the trendsetter in news coverage.” Neville and Gordon contend that a new era in television journalism was launched by the Buckley-Vidal debates.