As I’ve been noting here, one key metric to determine whether the prolonged GOP nomination process is damaging Mitt Romney’s general election prospects is his standing among independents, many of whom remain sour on Obama’s economic performance. Today’s new Pew poll offers another installment. The topline is striking enough — it finds that Rick Santorum is surging among Tea Partyers and conservatives, again suggesting that they just can’t come to terms with Romney as the nominee.