There are three Judy Garland authorities that Roadside Attractions would most obviously want on board their Oscar campaign for “Judy” and its star, Renee Zellweger: Liza Minnelli, Lorna Luft and Rufus Wainwright.

Granted, unlike Garland’s two daughters, Wainwright isn’t a relative. But his 2007 album, “Rufus Does Judy at Carnegie Hall,” is widely respected as the ultimate tribute to Garland and her legendary 1961 concert at the same historic theater in New York City, which some industry veterans of a certain age still tout it as “the greatest night in show business history.” (Luft gave his fandom her endorsement by appearing with Wainwright and the orchestra to sing “After You’re Gone” at his Carnegie Hall tribute.)

“I have a certain stake in it, I suppose,” Wainwright said — as something of an understatement — of his connection to Garland’s legacy, when Variety caught up with him at the 50th anniversary celebration of the Los Angeles LGBT Center. “I mean, I have been a trooper for Judy.” To prove the point, later that night he channeled his idol for an epic cover of “Somewhere Over the Rainbow,” which over the years has emerged as an escapist anthem for the marginalized community.

He lent his imprimatur to the “Judy” film in a very prominent way by agreeing to duet with the leading lady on “Have Yourself a Merry Little Christmas,” for the film companion album that Decca Records released over the weekend — a putative soundtrack that might well be instead titled “Zellweger Does Judy,” since a lot of the recordings are distinct from what’s actually heard in the film. So did Bridget Jones pull it off in his opinion?

“She does her own singing,” Wainwright said of Zellweger’s bold decision. “She doesn’t have Judy Garland’s voice. Nobody has Judy Garland’s voice. But it really is remarkable how high she flies — and in that stratosphere.” Which was Wainwright’s way of commenting on Zellweger’s vocal stylings while respectfully honoring the mythology of her character.

“I have to say her performance is pretty impeccable,” Wainwright quickly added, referring to the Oscar buzz. “And mainly because she just inhabits the role. She becomes Judy, and it’s not an imitation. It’s not a caricature. She really goes there.”