Romney adds to big delegate lead with clean sweep

WASHINGTON – Mitt Romney is adding to his big lead in the race for convention delegates by sweeping Republican presidential primaries in Maryland, Wisconsin and the District of Columbia.

The former Massachusetts governor won at least 74 delegates in Tuesday's contests, with 21 delegates yet to be decided. Romney got all 16 delegates in the District of Columbia.

He won at least 28 delegates in Maryland and at least 30 delegates in Wisconsin.

Nine delegates were yet to be decided in Maryland, and 12 were still undecided in Wisconsin.

Tuesday's contests marked the midway point in the race for convention delegates.

Romney leads the race for delegates with 646. His closest rival, Rick Santorum, has 272. It takes 1,144 delegates to win the GOP nomination for president.