John Bullock, a professor of political science at Towson University, said he believes county Republicans will be looking for electability over ideological purity. "The conservative bona fides matter, but you want someone who's going to have a decent shot at winning," he said.

Among the Democrats, all three campaigns are seeing hopeful signs.

Joanna Belanger, Mizeur's campaign manager, said the Montgomery County lawmaker has been courting Baltimore County voters since the first week of her campaign. She said Mizeur has 25 volunteer organizers at work in the county and expects to have an ad on TV in the Baltimore market soon.

Belanger said Mizeur is stressing a theme of "making sure the middle class is represented in Annapolis." The campaign strategist said she does not see a need for a specific message tailored to Baltimore County.

"Most people in Maryland are concerned about the same things," Belanger said.

In some ways, the Democratic race seems to be defying stereotypes.

Brown has racked up endorsements from old-line Democratic clubs and county elected officials on the east side, where so-called Reagan Democrats defected in large numbers to Ehrlich in 2002. Brown's county campaign co-chairs include Councilman John Olszewski Sr. and Sen. Kathy Klausmeier, east-side officials who are more moderate in their politics than Brown or Gov. Martin O'Malley.

While Brown is African-American, Gansler has earned the endorsement of the county's only African-American senator, Delores Kelley, and her 10th District Democratic Club on the west side. Mizeur, meanwhile, is making inroads in Towson and the Catonsville area, where two active Democratic clubs recently endorsed her by wide margins after hearing from all three of the party's candidates.

Brown, however, held the clear early advantage. In February, a Baltimore Sun poll found him leading Gansler by a 2-1 margin in the county.

Kelley's support notwithstanding, the African-American vote in the U.S. 40 and Liberty Road corridors will likely be an important advantage for Brown, the son of Jamaican and Swiss immigrants. The black population in Baltimore County is close to 30 percent of the total, but the African-American proportion of Democratic primary voters could reach 40 percent to 45 percent, said Herbert C. Smith, professor of political science at McDaniel College and co-author with Willis of "Maryland Politics and Government."

Olszewski, who is one of four Democratic County Council members backing Brown, said the lieutenant governor has already received the backing of the County Seal and Battle Grove Democratic clubs. He thinks Brown will do well on the east side, largely because of his Army service, which included a tour of duty in Iraq.

Ron Yeatman of Edgemere, president of the County Seal club and a candidate to succeed the retiring Olszewski, said Brown has been in southeastern Baltimore County often and has been well received.

"He's a vet. People respect that," Yeatman said.

Basu said Baltimore County is especially critical for Gansler because Brown is expected to easily carry Baltimore City and his home county of Prince George's. He said Gansler is expected to do well in Montgomery, but that won't be enough.

"The Gansler camp," Basu said, "has got to know that Baltimore County has got to be a big win for them."