Virginia officials say that a ballpark in suburban Washington would average thousands more fans per game than one in the city and have crafted a financial plan that banks on a Northern Virginia team being among the most successful in Major League Baseball.

The ambitious attendance projections by Virginia officials allowed them to dramatically improve their financing package in the weeks before they offered $285 million in government funding toward a ballpark last month. That amounted to $10 million more than a bid from D.C. officials, who assumed baseball's average stadium attendance of 2.4 million a year -- about 400,000 fewer than the Virginia group did.

The approach heightened the risk to Virginia taxpayers, who could be asked to cover any shortfall if a team didn't draw fans at a pace similar to those of high-drawing teams such as the New York Yankees, Seattle Mariners and San Francisco Giants, sports analysts said.

The Virginia group justified its optimistic projections to Major League officials by saying that the families that make up baseball's core clientele would be more likely to attend games in Northern Virginia than in Washington. A baseball source said the argument reinforced concerns about the city's ability to draw fans from the affluent suburbs that surround it.

"People from Virginia are not going to go into D.C. in the evening," Del. Vincent F. Callahan Jr. (R-Fairfax), chairman of the House Appropriations Committee, said in a recent interview. He was a member of the delegation to a baseball meeting in Phoenix last month.

He said that suburbanites' concerns about the city include traffic and crime and that the Virginia group presented statistics showing that attendance by Virginians at Washington Capitals games falls off on weeknights. The group also provided income breakdowns highlighting the wealth of Northern Virginians, whose median household income is $72,800, compared with $40,127 for city residents, according to the 2000 Census.

D.C. officials scoffed at the idea that suburbanites would stay away from a ballpark in the city. They said the District's booming downtown real estate market and the success of MCI Center show that Washington is a popular destination for people from across the region.

"Obviously, this is a place where people want to be," said Tony Bullock, spokesman for Mayor Anthony A. Williams (D). "There are plenty of District residents who don't want to cross the river to Northern Virginia because of traffic and other issues."

Beneath the swap of insults are different approaches to paying for a baseball stadium estimated to cost $400 million. The two groups are bidding against each other and against Portland, Ore., for the chance to become the new home of the Montreal Expos for the 2004 season.

The D.C. plan, which officials have declined to make public, would rely on a mix of taxes on players, fans and businesses to raise $27 million a year, enough to cover annual debt payments on a $275 million construction bond, according to sources familiar with the plan.

Tickets, merchandise and parking at the stadium would be subject to a 10 percent tax, and players would pay an income tax, although that would require action by Congress because the city's Home Rule Charter forbids taxing non-residents.

The rest of the money, $10 million to $12 million a year, would come from a levy on the gross receipts of businesses. It is the largest offer of a broad-based source of tax revenue -- meaning that the money otherwise could be used for schools, libraries or police -- by any group seeking the Expos.

The proposed use of broad-based revenue has drawn skepticism from the D.C. Council and criticism from opponents of public stadium financing.

"The mayor and his economic development officials are willing to go to great lengths to use general revenues for economic development projects that could be used for services," said Ed Lazere of the D.C. Fiscal Policy Institute.

The Virginia package, by contrast, would derive all but $1.5 million a year from sources related to the stadium itself. The sources include an admission tax of 10 percent, taxes on the income of players and team officials, taxes on sales at the stadium, rental of the stadium for other events and rental of retail shops.

In the weeks leading up to the presentation in Phoenix, Virginia baseball officials said that revenue from such sources, which already had been approved by the state General Assembly, amounted to about $10.5 million, half of the annual debt payments on a stadium.

But behind closed doors, they revealed new financial projections to Major League Baseball officials. Suddenly, those same sources were worth an estimated $19 million. Virginia's only broad-based revenue source would be a tax on hotel occupancy or car rentals in Alexandria and in Arlington and Fairfax counties.

The entire package was to generate $20.7 million a year at first and more later on. Virginia officials said that would be enough to borrow $285 million because the state enjoys a superior bond rating, enabling it to borrow on better terms than the District gets.

The shift allowed the Virginia group to portray its package as nearly complete.

Driving the new estimates were assumptions more optimistic than those D.C. officials were using. Attendance estimates are crucial because they determine projections for admission and sales taxes at the stadium and for team revenue. A team with higher ticket sales also may pay its players and officials more, generating additional income tax revenue, too.

The Virginia group assumed 3.2 million fans, or nearly 40,000 a game, in the first year, with attendance declining to 2.8 million a year in five years.

"This is one of the larger markets in the country, and I think that a 2.8 million average is definitely viable given the size of the market," said Gabe Paul Jr., executive director of the Virginia Baseball Stadium Authority.

But Max Muhleman, president of IMG/Muhleman Marketing Inc., a sports consulting group, said the Virginia projection "certainly is optimistic."

Only four of 30 Major League teams reached 3.2 million fans last year, and only seven reached 2.8 million. Even the Baltimore Orioles, with a history of high attendance at Camden Yards, saw the total drop to 2.7 million in the fourth year of fielding mediocre teams.

D.C. officials, by contrast, assumed 3.1 million fans in the first year and 2.4 million a year over the long term. The latter figure represents an average of 30,000 fans per game, compared with 34,568 for Virginia. The Virginia group also assumes an average ticket price of $26, compared with $22 for the D.C. group. The Major League average last year was $18.69.

Virginia officials say their construction borrowing would be issued by a state authority with bonding power, not the state itself. But Callahan acknowledged that the state might feel a "moral obligation" to rescue a Virginia bond before allowing it to default.

Major League Baseball cares little about the reliability of financial projections in stadium financing packages, said an official speaking on the condition of anonymity. Any shortfall would be the responsibility of the taxpayers who are paying the bill.

"It may make a difference for whoever's got to pay the bond eventually, but it doesn't make any difference to us," the baseball official said. "How they choose to believe . . . they can raise the revenues to service the debt and the bonds is really their problem, not ours."

Staff writer Timothy Dwyer contributed to this report.

Del. Vincent F. Callahan Jr. (R-Fairfax) said people from Virginia don't want to go to the District for a night game.Virginia's attendance projections are "definitely viable given the size of the market," said Gabe Paul Jr. of the Virginia Baseball Stadium Authority.