washington former u.s. republican presidential nominee endorse marco rubio race party presidential nomination huffington post report sunday endorsement come heel rubio second-place finish saturday night primary south carolina edge rival ted cruz slot website report cite unidentified republican source romney join list so-called establishment endorsements back first-term u.s. senator florida include south carolina governor nikki haley endorse rubio days state primary report alana wise edit doina chiacu article fund part sap independently create reuters editorial staff sap editorial involvement creation production romney endorse rubio 2016 republican white house race report