GREENVILLE, S.C. - Republican presidential candidate Rick Santorum sharpened his messages of populism and electability in South Carolina Saturday morning, saying "the grandson of a coal miner" is better equipped to relate to blue-collar voters in swing states than "a Bain executive." As Santorum's adversaries in the GOP field - particularly former House Speaker Newt Gingrich and Texas Gov. Rick Perry - have attacked front-runner Mitt Romney's record at the private equity firm Bain Capital, Santorum has taken a pass, repeatedly saying he would not attack the capitalist system. Then today, the former U.S. senator from Pennsylvania struck the theme...