Proponents of progressive policies might recall that, in 2008, U.S. presidential candidates Barack Obama and Hillary Clinton espoused the belief that marriage should be between one man and one woman. 

As those towering leaders evolved, other public figures may as well.

Enter Martina Navratilova. The equal-rights advocate and tennis legend has a long history with the topic of sexual orientation in sport, and a complicated past and present with matters of transgender inclusion. The public kerfuffle over her early-2019 comments about trans athletes, which led to LGBTQ-centric nonprofit Athlete Ally severing ties with her as an ambassador, catalyzed a new opportunity.

Navratilova is hosting a new documentary for the BBC, with an SEO-friendly title: The Trans Women Athlete Dispute With Martina Navratilova. Therein, she speaks with trans women, athletes who identify as trans or cisgender (cis, for short), and scientists.

In the past, the 62-year-old has said that trans athletes should not be allowed to compete in professional sports during their transitions or after gender-confirming surgeries. After initial walking back her comments, she then filed a Sunday Times opinion column positing that allowing trans women to compete in pro sports was "insane" and tantamount to "cheating."

Navratilova remains on a journey, and while the 18-time major singles champ does not, in the documentary, frame matters in terms of "trans" and "cis", she does want to learn more. She wants to grow in her understanding, and she's listening.

In the 58-minute docu-film, Navratilova shares her relatively newfound conclusion. You'll have to view it to consider the full context of her position, though in a media interview, she said, "I realized perhaps I don’t know as much as I thought! I have no dog in this fight other than wanting to fight for equality and fairness."

Skeptics about Navratilova's perspective, her evolution, remain. One of those is Christina Kahrl, an ESPN senior editor who oversees Major League Baseball coverage and who is herself a trans woman.

Navratilova's Twitter feed remains hyper-political, as she sounds out at-length perspectives and short-form quips in equal measure. She has not, however, said much more about her documentary than the above response to Kahrl.

Per Owl Fisher's column for The Guardian, "As Navratilova herself touches upon in the documentary, there are no trans people competing at an elite level of sport such as at the Olympics, and no sign of trans women dominating in women’s sport, despite the fact they have been allowed to compete under certain conditions since 2003."

Times will change, of that we can be sure. History has shown us that, and now Martina Navratilova does, too.

Follow Jon on Twitter: @jonscott9.