WATCH: Which Transphobic Slur Did Joan Rivers Call Michelle Obama?

The insult comic continues a long tradition of joking that certain cisgender women are actually transgender as a way of putting trans women down, taking aim at First Lady Michelle Obama.

In a brief video reportedly shot earlier this week in New York, 81-year-old Joan Rivers calls First Lady Michelle Obama "a transgender," joking that this makes Barack Obama the first gay president.

After being asked about the U.S.'s likelihood of having either a woman or a gay president in the near future , Rivers replied, "We already have that with Obama. You know Michelle is a tranny."

The unidentified journalist tries to clarify, asking, "I'm sorry. She's a what?"

"A transgender," Rivers replies. "We all know."

Conservatives have long made jokes insinuating that the First Lady is actually a transgender woman, but it's not often that a liberal-minded comedian — let alone one who credits much of her success to her devoted LGBT fan base — make this type of uninspired joke.

Similarly, liberal individuals have often joked that Ann Coulter is transgender. These types of "jokes" are designed to suggest that being trans is something to be ashamed of.

Referring to cisgender (nontrans) women as trans "only furthers the marginalization of women and transgender people," wrote Vincent Paolo Villano of the National Center for Transgender Equality in a 2012 op-ed for The Advocate.

"Judgments against Ann Coulter because of how she looks are also an attack on transgender people," Villano wrote later in that op-ed. "The difference is transgender people often can’t shrug their shoulders and move on the way Ann Coulter can. Indeed, this kind of prejudice has a role in the staggering rate of suicide attempts among transgender people: 41% (compared to 1.6% of the general population). While Ann Coulter gets to stir controversy like it’s a game, everyday transgender Americans have to deal with the bias and violence at the core of these messages."

It should be noted that even if Mrs. Obama was a transgender woman, that would not make the President gay.

Watch the exchange below: