Mitt Romney’s supporters on Capitol Hill are giving him political cover for the healthcare plan he signed into law as governor, even as his competitors for the GOP presidential nomination ramp up their attacks on “RomneyCare.” Romney’s healthcare reform initiative in Massachusetts is viewed as one of his biggest political liabilities going into the Republican primary, due to its similarities to President Obama’s healthcare overhaul. But leading conservatives, including supporters of Romney during his 2008 presidential run, argue that the Massachusetts plan isn’t a deal-breaker. “One of the reasons I endorsed Romney [in 2008] is his attempts to make private...