Former House Speaker Newt Gingrich enjoys a home-field advantage in the race for the Georgia presidential primary, but he trails Mitt Romney in head-to-head matchups with President Barack Obama, a new poll shows. Gingrich, a former Georgia congressman, leads Romney 43 percent to 21 percent among Georgia Republicans, according to the poll by Mason-Dixon Polling & Research for The Atlanta Journal-Constitution and the Georgia Newspaper Partnership. No other candidate drew double-digit support. The poll shows Republican voters continue to express concern over the state of the economy as the March 6 presidential primary draws closer. Nearly half of all respondents...