WASHINGTON (AP) - Mitt Romney has added to his big lead in the race for convention delegates by winning the Maryland Republican presidential primary.
Romney won at least 28 delegates in Maryland, with nine left to be awarded.
Voters also went to the polls Tuesday in the District of Columbia, with 16 delegates at stake, and Wisconsin, where 42 delegates were up for grabs.
Romney leads the race for delegates with 600. He is on pace to reach the number of delegates needed to clinch the nomination - 1,144 - in early June.
Romney's closest rival, Rick Santorum, has 272 delegates. Santorum would need 76 percent of the remaining delegates to clinch the nomination before the party's national convention - a nearly impossible task because most states award delegates proportionally.