National Portrait Gallery Director Martin Sullivan, who weathered a political storm after Secretary of the Smithsonian G. Wayne Clough censored an artwork on display in the museum’s “Hide/Seek” show in late 2010, is stepping down for health reasons. The museum’s curator of prints and drawings, Wendy Wick Reaves, will serve as acting director while a replacement is sought.

Sullivan, who has been the director of the museum since 2008, might have stepped down in 2010 after Secretary Clough pulled a film by David Wojnarowicz from the museum over his objections. Sullivan didn’t. When the scandal first broke, the Smithsonian Institution peddled the line that the decision to remove that video was amutual decision by Clough, Sullivan, exhibit co-curator David Ward, and Smithsonian undersecretary for art, history, and culture Richard Kurin. At the time, Sullivan appeared to bristle at the suggestion that he would have elected to remove the video, but he did not refute the official story. Later, Tyler Green confirmed that the decision to censor the show of works by queer artists was Clough’s alone.

By its nature, the National Portrait Gallery is one of the Smithsonian’s most conservative institutions. It organizes artworks by subjects, emphasizing the biographical elements of the people who appear in its portraits, rather than organizing them by artist or mode of art (as most art museums do). It’s an art museum as a history museum—or as a kind of celebrity slideshow. Yet no Smithsonian museum had a bigger impact in 2010.

The “Hide/Seek” fiasco has in some ways been good for the Smithsonian: Anti-gay conservative activists got away with swift-boating the institution once, but the Smithsonian’s now inoculated against another similar effort. And the nonbigoted art world (that’s most of it) rallied and organized, especially locally. But the incident has cast a long shadow over the Smithsonian.

That’s a thing for the Smithsonian to think about it with its appointment to replace Sullivan. The Smithsonian rebuked Clough, but it has fallen short of sending a message throughout the system that courage in the face of intolerance is a characteristic America’s cultural treasury demands of its employees. A staffer at the National Museum of American History told me Smithsonian Institution brass screened its small summer 2011 exhibit on HIV for certain materials critical of President Ronald Reagan’s handling of the emerging HIV epidemic; in the Post, Jacqueline Trescott reported on scrutiny over the exhibit. It would be easy to imagine a replacement for Sullivan that sent the message that curators should keep their heads down and put out shows that don’t challenge the status quo. The National Portrait Gallery does too much of that already.