Mitt Romney won easy victories in Massachusetts, Virginia and Vermont Tuesday as he looked to take a commanding lead in the Republican presidential race. Newt Gingrich, hoping to revitalize his campaign, notched a home-field win in Georgia. Together, 10 states scattered across the country hosted Super Tuesday contests, the biggest day yet in the fight for the right to challenge President Barack Obama this fall. Ohio, a critical state in the general election, was the spotlight race, with Mr. Romney running close to former Sen. Rick Santorum, who has seen his Ohio lead erode. The former Pennsylvania senator was hoping...