Mitt Romney won nearly all the convention delegates a three-primary sweep, adding to a lead that will be insurmountable without a dramatic shift in the race for the Republican nomination for president.
With 95 delegates at stake Tuesday, the former Massachusetts governor picked up 86 delegates in Maryland, Wisconsin and the District of Columbia. His chief rival, former Pennsylvania Sen. Rick Santorum, won the other nine delegates, all in Wisconsin.
Tuesday's contests marked the midway point in the race for convention delegates.
Romney has 658 delegates, including endorsements from members of the Republican National Committee who automatically attend the August convention in Tampa, Fla., and can support any candidate they choose.
Romney has won 58 percent of the primary and caucus delegates so far. That puts him on pace to reach the 1,144 delegates needed to clinch the GOP nomination on June 5, when voters go to the polls in five states, including delegate-rich California and New Jersey.
Santorum has 281 delegates. He would need 80 percent of the remaining delegates to win the nomination before the party's national convention in August. That won't happen as long as Romney stays in the race because most upcoming primaries use some type of proportional system to award delegates, making it hard to win large numbers of delegates in individual states.
Former House Speaker Newt Gingrich has 135 delegates and Texas Rep. Ron Paul has 51.
Santorum's best hope to win the nomination is to prevent Romney from reaching 1,144 delegates, forcing a contested convention.
Santorum's campaign argues he would fare well in a contested convention because delegates would gravitate toward the more conservative candidate. Santorum says the contest is only half over, and he has no intention of getting out.
Romney is increasingly focusing on the general election campaign against President Barack Obama. In a speech to newspaper editors and publishers Wednesday, Romney criticized Obama's handling of the economy, government benefit programs and national defense. He didn't mention Santorum.