NBC: Santorum Wins La. Primary By Significant Margin Sean Gardner / REUTERS Republican presidential candidate and former U.S. Senator Rick Santorum signs placards as he greets supporters at a Get Out The Vote rally in Mandeville, Louisiana March 21, 2012. By Michael O'Brien Rick Santorum’s campaign netted a victory Saturday night in Louisiana, where NBC News projected he’d won that state’s GOP primary by a significant margin. The win sparks hope of a campaign rebound, following Santorum’s lopsided losses to Mitt Romney in the Illinois and Puerto Rico primaries. The former Massachusetts governor finished second and Newt Gingrich third in...