WASHINGTON (Reuters) - Arizona Sen. John McCain, taking the first step toward a 2008 White House bid, said on Thursday a return to principles of limited government and "common sense conservatism" would carry Republicans back to power after last week's election drubbing. "We lost our principles and our majority. And there is no way to recover our majority without recovering our principles first," McCain told the Federalist Society, a conservative legal group, in the first of two high-profile speeches kicking off his expected presidential campaign. McCain, an early favorite in what promises to be a crowded Republican presidential field, filed...