Various media outlets are making much of a story about the Deutsche Oper being forced to reschedule a gala performance of Wagner's Rienzi that would have coincided with Hitler's birthday. Amplifying the outrage are claims that Rienzi was "Hitler's favorite opera," "Hitler's favorite Wagner opera," or, more oddly, "Hitler's favorite Wagner production." I recall James Jorden some time ago skeptically cataloguing contradictory statements about Hitler's Lieblingsoper, though I can't seem to find the post. In any case, typing the relevant phrases into Google shows the problem. The special opera is said to have been Rienzi, Die Meistersinger ("probably Hitler's favorite," Ernst Hanfstaegl said), Götterdämmerung, Tristan, Parsifal, Lohengrin, Eugen d'Albert's Tiefland, and The Merry Widow. To avoid trouble, German opera houses may have to avoid programming any of these works on April 20.
The main thing that is known about Hitler and Rienzi is that a 1905 performance of the opera in Linz inspired him to begin thinking of a political career. Hitler identified strongly with Wagner's portrayal of the "people's tribune" — a nobler figure than the ultimately decadent demagogue of Edward Bulwer-Lytton's novel — and drew political lessons from Rienzi's defeat, as Hans Rudolf Vaget, the brilliant Thomas Mann scholar, has noted. In the essay "Hitler's Wagner," which appears in the anthology Music and Nazism, Vaget observes that in 1930 Hitler evidently spoke to Otto Wagener of his "special liking" for Rienzi. (Wagener had assumed that Hitler wouldn't care for the opera because it shows a popular leader falling prey to intrigues. They were deciding whether to see Rienzi or Rosenkavalier.) And, yes, the autograph manuscript of Rienzi may have gone with Hitler to the bunker, along with the original scores of Die Feen and Das Liebesverbot and various manuscripts related to the Ring. (Interestingly, though, Sven Friedrich, the director of the Wagner archive in Bayreuth, believes that this material stayed at Hitler's villa in Berchtesgaden, and may still resurface.) So Rienzi had a powerful, even pivotal, effect on Hitler. But there is no basis for calling it his "favorite opera."
In the end, the question should be left unanswered: in the case of Hitler, above all others, we should not assume more knowledge than we have. The documentary record does hint, however, that Hitler, like so many others, may have been most deeply affected by Tristan — ironically, the least "political" of the music dramas. In a notebook from Landsberg prison, Hitler wrote that he was “dreaming of Tristan and his kin." In January 1942, according to Monologe im Führer-Hauptquartier, 1941-1944, he said, "Tristan is surely [Wagner's] greatest work. We have the love of Mathilde Wesendonck to thank for it." (“Der Tristan ist doch sein grösstes Werk. Es war die Liebe zur Mathilde Wesendonck, der wir das verdanken.”) And Hitler's secretary Christa Schroeder recalled him saying that he wished to hear Tristan when he died. He had a primal encounter with Tristan at the Vienna Court Opera in 1906; years later, in conversation with the director Alfred Roller, he could describe the production in detail. In 1998, while working on a piece about Wagner and anti-Semitism for The New Yorker, I puzzled over the fact that extant descriptions of the episode in the Hitler literature did not name the conductor. So I sent a fax to the Staatsoper, asking who led Tristan on May 8, 1906. It was, unsurprisingly yet shockingly, Gustav Mahler.