Newt Gingrich leads Mitt Romney among Republicans, he is the weakest of the Republican candidates tested against President Obama, according to an NBC News-Wall Street Journal poll released Thursday evening. Gingrich leads Romney 37 percent to 28 percent nationally among registered Republicans likely to vote in the primaries; Rick Santorum is in third with 18 percent, and Ron Paul is fourth with 12 percent. Gingrich has built its advantage by consolidating the heart and soul of the Republican party: very conservative voters, the South and the Tea Party. Though Gingrich is the preferred candidate of GOP primary voters, though, he...