Cher’s “Believe” set off a trend for electronically tweaked vocals while bamboozling listeners into questioning their own trust in love. It was a revolutionary act for a fiftysomething camp icon with serious credibility issues — a bizarre and rather lovely accident. Living Proof endeavors to make lightning strike twice in the same place. Repeating the synthesized hiccups, stirring Europop tunes and anxious up-tempo digital beats of Believe, Living Proof gets the job done well. Unlike house music or modern R&B, Cher’s twenty-first-century disco is built on fully fleshed songs and detailed arrangements, and the studio wizardry is even grander than before. But Living lacks its predecessor’s unexpected impact. “Song for the Lonely” clearly intends to evoke September 11th, and other tracks such as “A Different Kind of Love Song” return to themes of tragedy, heroism and universal brotherhood. Coming from a willfully wiggy billion-dollar diva, this noble stuff feels calculated, particularly when it’s presented in such a sparkling, showbizzy package. Cher believes in love — no problem. Convincing us she’s a selfless social commentator demands a much taller leap of faith.