At Centennial Park in Howard County yesterday morning, Tucker McConville, 15, was taking batting practice from his father, Hugh, on Field No. 4. That's 17 miles from Camden Yards, home of the Baltimore Orioles. It's 29 miles from Robert F. Kennedy Memorial Stadium, where a baseball team will play initially if Washington wins the bidding for the Montreal Expos.

Should that happen, which team would claim these two fans?

Demographically, Howard and Anne Arundel belong to Baltimore. Three-quarters of their populations work in the Baltimore area, and roughly one-fourth has seen at least one Orioles game in the past year, according to a recent demographic study by Scarborough Research. Since the 1950s, the team has broadcast its games in the two central Maryland counties, targeted them with its advertising and embraced their residents as loyal fans.

Hugh McConville of Catonsville grew up with the Orioles, an American League team. He's a reminder of why "fan" comes from "fanatic." He goes to Oriole Park at Camden Yards maybe five times a season and watches 120 more Orioles games on television. Even so, the Expos' coming to Washington works for him -- and works for baseball, he said.

"I could become an Expos fan because they're a National League team," McConville said. "To me, there could be nothing better for the area, economically, than for the Expos to play the Orioles in the World Series."

Like his dad, Tucker McConville roots for the Orioles. But his loyalties are a little more defined by players. If the Expos, for example, were able to lure his favorite player, shortstop Nomar Garciaparra of the Chicago Cubs, then he'd be dragging his dad to RFK.

If Major League Baseball awards the Montreal Expos to Washington, then Anne Arundel and Howard counties, which have a total of 738,000 people, undoubtedly would become prime marketing targets for the new team. And Orioles owner Peter G. Angelos isn't the only one who thinks that could hurt his franchise.

"We've got this beautiful ballpark here. It's just sad to think about it being empty," said Karen Holloway, 48, of Columbia as she watched the Orioles beat the Detroit Tigers on Friday night in Baltimore.

Orioles spokesman Bill Stetka said there's been no discussion by his organization about how a Washington team would affect the Orioles' marketing plans. But it seems nearly everybody else has had numbers to show how much, or how little, a Washington team would hurt the Orioles in the region's fast-growing suburbs between Baltimore and the District.

Brian Hannigan, spokesman for the Virginia Baseball Stadium Authority, which is trying to persuade Major League Baseball to move the Expos franchise to Northern Virginia, said that people in Central Maryland would be less likely to travel to his area to see a game. Consequently, he said, a team in Washington "would take a greater chunk out of (the Orioles') fan base than if the team were located in Northern Virginia."

Bill Hall, a negotiator for the D. C. Sports & Entertainment Commission, which is leading the District's push for the team, said true baseball fans won't have to choose -- that they can see both teams.

"I grew up in New York, and I was certainly both a Yankees and a Mets fan," he said. "I think that would happen here, as well. Having teams in the different leagues allows fans to root for their favorite team in each league."

Major League Baseball plans to avoid overlapping home games in Washington and Baltimore, Hall said.

It's like the real estate adage, he said: "One store on a street corner is good -- but two is better."

But swearing allegiance to a baseball team, true fans said, bears no resemblance to deciding whether to visit the Inner Harbor or the National Zoo on a weekend. Team loyalty is born into families, nurtured in the neighborhoods, hardened through years in the stands.

That's the case with McConville, a 54-year-old forklift operator. But he's trying to save money for Tucker's college education, so he's not planning to see that many more baseball games, whether in Baltimore or Washington. It costs $150 to take his family to Camden Yards, not counting hot dogs and beer, he said.

"If you put a team in D.C., they will be supported by everyone -- but especially the wealthy," McConville said. "I can't imagine what they're going to charge."

At the Champps sports bar and restaurant in Columbia -- 32 miles from RFK, 19 miles from Camden Yards -- Rich Stokes, 56, also doubted that he would drive to the District to see the new team play. But he said other people in Howard County, especially those who have government jobs in the District, might help fill a new ballpark in Washington.

"My guess is, location of work would have a lot to do with it, and a lot of people do work for the federal government, so that would help,'' he said. "I'd say the average guy from here is going up to Oriole Park."

Dennis Lowry, 45, a self-employed graphic designer who was eating at Champps, said: "I'd love to see D.C. get the Expos. I think they deserve a baseball team."

But nothing would dilute his loyalty for the Orioles, Lowry said. His wife, Sandi Lowry, 45, a lifelong Marylander who roots for the Orioles and the Redskins, said she shared that sentiment.

A sports team, she said, "gives definition to a place."

Besides that, she said, "it's something to root for."

Staff writer Eli Saslow and senior marketing researcher Dave Barie contributed to this story.

"I could become an Expos fan because they're a National League team," says Orioles fan Hugh McConville, 54, of Catonsville, tossing batting practice to his son at Howard County's Centennial Park."I'd love to see D.C. get the Expos. I think they deserve a baseball team," says Dennis Lowry, with wife, Sandi, at the Champps sports bar in Columbia.