Hopefuls compete for Md., Va., D.C.

McLEAN, Va. -- Tuesday's "Potomac primary," with large pockets of black and highly educated voters who have thus far favored Barack Obama in the Democratic race, looks like inhospitable territory for Hillary Rodham Clinton. But she's not conceding the region.

"It's a matter of delegates," said Mark Rozell, a public policy professor at George Mason University in Arlington, Va. "Even though she's likely to lose the popular vote, there's a real incentive for her to try to boost her numbers and increase her delegate count."

Both Democrats are advertising in Virginia, Maryland and the District of Columbia in the run-up to the Potomac primary. Obama held a series of town halls and rallies, and he planned rallies at sports arenas today in Baltimore and at the University of Maryland. Clinton's schedule has her touring a plant today near Baltimore and speaking to a University of Virginia government class in Charlottesville. Her husband, former president Bill Clinton, spent Sunday morning at black churches in Washington and Maryland.

The message from both candidates Sunday was "I care." Obama discussed his education plans with parents in Northern Virginia. Clinton released a raft of statistics designed to show how her economic plan would benefit Virginians.

Virginia is the hot contest on the Republican side. Arizona Sen. John McCain was capping today with a rally in Richmond. Former Arkansas governor Mike Huckabee scheduled a whirlwind of Virginia rallies.

McCain has piled up Republican endorsements, including those from former Maryland governor Robert Ehrlich and former Virginia senator George Allen. The Democratic establishment is divided, as Clinton dominates in Maryland and Obama in Virginia.

Maryland Gov. Martin O'Malley crisscrossed the state Sunday on Clinton's behalf. He'll also join her today at a plant that makes transmissions for GM hybrid vehicles. Clinton has pledged more "green collar" jobs to help develop alternative energy, and O'Malley said that message resonates.