Joe Biden couldn't help dropping an f-bomb when President Obama signed the Affordable Care Act. Obama knew he would have "more flexibility" in his dealings with Russia after he was reelected. And back in 2010, Carly Fiorina didn't like Barbara Boxer's hairstyle.

Those are just a few things we've learned from hot mics over the years, and now we have a new one: Sen. Lindsey Graham is a "bro with no ho," in the words of Illinois Republican Sen. Mark Kirk.

The incident, caught by Huffington Post's Sam Stein , occurred during a Thursday Appropriations Committee markup session. Kirk can be overheard, at around the 25-second mark, telling a fellow lawmaker that he had been joking recently, "He's going to have a rotating first lady. He's a bro with no ho."

Kirk was referring to Lindsey Graham's recent comments about who would serve as first lady if he were elected president. Graham, a lifelong bachelor, recently told the Daily Mail that he could have "a rotating first lady" as president, or that his sister could fill the role.

Graham is one of many running for the GOP presidential nomination in 2016, but he is the only who is a bachelor. In fact, if he were elected president, he would join a tiny club of bachelor presidents.

Graham would be only the third person to become president as a bachelor — James Buchanan, who assumed office in 1857, was the only president to remain a lifelong bachelor. Grover Cleveland, inaugurated in 1885, was also solo when he entered the White House — and he makes Graham's suggestion that his sister serve as first lady seem a little less odd. Cleveland's sister, Rose, served as hostess in the White House for a little over a year, until her brother married Frances Folsom (another fun fact: he was 49 at the time; she was only 21 ).

As HuffPo's Stein points out, Graham has shrugged off questions of whether an unmarried president might be unrelatable to many voters.

Really, an unmarried president might be more relatable than ever. A growing share of Americans are unmarried, and as the Pew Research Center found last year, a record number also , like Graham, have never been married.

Being single may not be a big worry for Graham, but the comment could be a problem for Kirk, who is facing a competitive reelection race next year. He may face former Rep. Joe Walsh in the primary, and Rep. Tammy Duckworth is running on the Democrat side.

Copyright 2016 NPR. To see more, visit http://www.npr.org/ .