Steve Granitz

Mary Bono is out as interim CEO and president of USA Gymnastics. Bono resigned from her post on Tuesday, just five days after she was appointed. 

The resignation comes after Bono faced mounting pressure and criticism questioning whether or not she was fit to lead the program. Several prominent USA gymnastics athletes -- including Olympians Simone Biles and Aly Raisman -- have publicly called out Bono and opposed her appointment in recent days.

Much of the criticism has come thanks to an anti-Nike tweet she sent in September. In that tweet, which has since been deleted, a photo showed that Bono used a black marker to cover up a white Nike logo on a pair of golf shoes -- a symbol of protest against Nike's polarizing "Just Do It" campaign featuring Colin Kaepernick

"Playing in a charity golf tournament raising money for our nation's Special Forces operators and their families. Unfortunately had these shoes in my bag," Bono tweeted along with the photo. "Luckily I had a marker in my bag too." 

Following Bono's appointment as interim CEO and president, Biles -- a Nike athlete -- helped bring attention to the tweet by quote-tweeting it with a message of concern.

After the tweet continued to garner attention and negative responses, Bono deleted it and issued an apology.

However, Bono seemed to take a different tone in the resignation statement she released Tuesday, defending the tweet and saying that she "nationally exercised [the] first amendment" in the same way that Kaepernick did. 

"My withdrawal comes in the wake of personal attacks that, left undefended, would have made my leading USAG a liability for the organization," Bono wrote.

The anti-Nike tweet wasn't the only cause of pushback against Bono's appointment. Raisman, who has arguably been the face of USA Gymnastics over much of the past decade, tweeted concern over the idea that Bono's law firm, Faegre Baker Daniels, may have had a role in enabling the sexual abuse committed by former USA Gymnastics team doctor Larry Nassar.

Earlier this year, Nassar pleaded guilty to child pornography charges and 10 counts of sexual assault of minors, which resulted in a maximum prison sentence of 360 years. Nassar was accused of molesting at least 250 athletes -- many of them minors -- under the guise of medical treatment. Among his accusers were several well-known Olympic gymnasts, including Raisman and Biles.

Former USA Gymnastics president and CEO Kerry Perry resigned in September as a result of the sexual abuse scandal. That led to this month's appointment of Bono, 56, who is a former GOP congresswoman from California . She is also the widow of late pop star Sonny Bono.