Cindy McCain, the wife of Arizona Senator John McCain, a Republican, has signed a petition asking the senator to back the Employment Non-Discrimination Act (ENDA), which seeks to prohibit workplace discrimination based on sexual orientation and gender identity.

ENDA cleared a Senate committee in July and a floor vote is expected as early as this month.

According to The Washington Post, Cindy McCain was approached by John Gomez, an HRC organizer, at a Staples in Phoenix.

“He talked with her about our efforts to pass ENDA, and she shared her support for the bill,” HRC spokesman Michael Cole-Schwartz told the paper.

Cindy McCain signed the postcard and addressed it to her husband, Cole-Schwartz said.

Republican Senators Mark Kirk of Illinois, Lisa Murkowski of Alaska and Orrin Hatch of Utah voted in favor of the bill in committee.

(Related: Procter & Gamble endorses federal LGBT protections bill ENDA.)