Every four years since 1988, the team behind the PBS series “Frontline” creates a film called “The Choice,” exploring the political biographies of the candidates running for president. By July of this year, filmmakers Michael Kirk and Mike Wiser had assembled a rough cut of a four-hour documentary about President Biden and former President Trump , two men of the same generation who were bracing for a rematch after the contentious 2020 election. “This thing was sprawling and big, but it was a hell of a story,” said Kirk, likening the project to the Michael Cimino epic “Heaven’s Gate.

” Then, on July 21, Biden announced he was dropping out of the race , and Vice President Kamala Harris quickly emerged as the presumptive nominee, a historic turn of events that upended the election — and forced the filmmakers to pivot in record time to create “ The Choice 2024: Harris vs. Trump ,” a two-hour documentary premiering Tuesday on PBS. In a stroke of luck, by the time Biden dropped out, they had already started work on a documentary about the vice presidential contenders — an idea “Frontline” executive producer Raney Aronson-Rath proposed because of the advanced age of the likely presidential nominees.

Still, it was a mad scramble to complete the Harris portion of “The Choice 2024,” particularly given the lack of documentaries and biographies about the vice president compared with her rival, who has been courting media attention for decades. “We just .