It was August 2004, several months after George W. Bush endorsed a controversial constitutional amendment that would prevent states from recognizing same-sex marriage. His vice president, Richard B. Cheney, did something bold.

He said he believed states ought to be able to sort the matter out for themselves.

“Lynne and I have a gay daughter, so it’s an issue that our family is very familiar with,” Cheney said during a town hall in Davenport, Iowa, according to a Washington Post story.

“With respect to the question of relationships, my general view is that freedom means freedom for everyone. People ... ought to be free to enter into any kind of relationship they want to.”

It wasn’t the first time Cheney expressed this opinion. But he had never before spoken so openly about his daughter Mary’s sexual orientation, which, almost 15 years later, figures prominently in Adam McKay’s splashy, somewhat satirical biopic, “Vice.”

At times, the film uses the father-daughter relationship to humanize him as he struggles to balance family and politics.

“I think you have to humanize him,” McKay recently told the New York Times about Cheney, “because unless you see how a regular human being can go down these roads, it’s useless.”

Mary first becomes a political factor in early 2000, when Bush (Sam Rockwell), the Texas governor who would soon become the Republican presidential nominee, asks Halliburton chief executive Richard Cheney (Christian Bale) to join the ticket. Cheney — who before joining the private sector had served as Gerald Ford’s chief of staff, Wyoming’s sole representative and George H.W. Bush’s secretary of defense — is unsure of whether he wants to return to public office and instead offers to head Bush’s vice-presidential search committee.

One of the potential reasons behind Cheney’s hesitation carries over from earlier in the film: He and Lynne (Amy Adams) want to protect Mary (Alison Pill), who came out to her parents in high school, from the public eye.

Cheney wasn’t “the most scintillating or exciting candidate,” said Matthew Dallek, a political historian at George Washington University. “He clearly brought other strengths to the ticket for George W. Bush.”

This isn’t to say the real-life Cheneys weren’t supportive of Mary, a conservative who would serve as her father’s director of operations for his and Bush’s reelection campaign. She wrote in her 2006 memoir “Now It’s My Turn,” according to an excerpt published in the Guardian, that her father made sure before committing to the ticket that she and the rest of the family were aware of what his decision to run with Bush would mean for each of them. Lynne was the most against the idea, according to Mary, while the Cheneys' older daughter, Liz, was all for it.

Mary wrote that she also had to consider the feelings of her partner, Heather Poe, whom she married in 2012.

Liz, meanwhile, had long opposed same-sex marriage — and in 2013, she reaffirmed that position on national television while running for a Senate seat in Wyoming, setting off a public spat. McKay recreates this scenario toward the end of “Vice,” depicting Richard Cheney as the one who gives Liz the green light to take a very public stance against her sister’s marriage.

“Vice” declares early on that it tries as best it can to depict factual events, given how opaque Cheney could be. Neither sister, nor their father, returned The Post’s requests for comment on whether this or other aspects of the film are accurate.

“I love Mary very much, I love her family very much,” the real-life Liz said to Fox News host Chris Wallace that November. “This is just an issue on which we disagree.”

Poe responded to the statement on Facebook: “Liz has been a guest in our home, has spent time and shared holidays with our children, and when Mary and I got married in 2012 — she didn’t hesitate to tell us how happy she was for us. To have her now say she doesn’t support our right to marry is offensive to say the least."

Mary shared the post, according to a Post story, and added, “Liz — this isn’t just an issue on which we disagree — you’re just wrong — and on the wrong side of history.”

Eventually, the parents stepped in with a public statement: “This is an issue we have dealt with privately for many years, and we are pained to see it become public. Since it has, one thing should be clear. Liz has always believed in the traditional definition of marriage."

Dallek, the historian, speculated that McKay positioning Richard Cheney as the one who orchestrated Liz’s statement felt like a reach. Liz is a “hard-right and pretty savvy political operator in her own right,” he said. She didn’t need anyone to tell her at the time that she had to be socially conservative — and therefore strongly opposed to same-sex marriage — to win the Republican nomination for Senate in Wyoming, he added.

What doesn’t make it into “Vice” is that Liz dropped out of the race the next January, citing health issues in the family. Then, a year after her younger sister publicly urged Republican leaders elected in 2016 to “embrace marriage equality,” Liz decided to run for Wyoming’s sole House seat instead.

She called representing Wyoming her “sacred duty” and, though refusing to comment further because of Mary, confirmed that her views on same-sex marriage remained the same. Liz won the 2016 election, as the end credits of McKay’s film state and this past November was elected House GOP conference chair — a position her father held three decades ago.

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