I recall hearing a taped interview on the radio some years ago with a nuclear physicist. He consistently pronounced the word "noo-cue-lar." When the tape finished, the board announcer made a bit of an aside that went out over the air. Reflected my thoughts exactly. He said, "When a man can't even pronounce the name of his own profession correctly, it makes you wonder just how competent he is. . . ."
I've heard the opinion expressed that Bush has been corrected on it many times and knows perfectly well how to pronounce the word, but he continues to use it in an effort to keep what Karl Rove considers to be "the Bubba vote."