J. Walter Tejada, an immigrant from El Salvador who became an Arlington activist and political organizer, also became the first Latino to win a countywide election last night, defeating Republican Mike W. Clancy in a special election to fill the County Board seat of Charles P. Monroe (D), who died in January.

With all 47 precincts reporting, unofficial returns showed Tejada with 55 percent of the vote to Clancy's 45 percent in an election that generated more votes than any County Board special election in Arlington's history. Nearly 18 percent of Arlington's approximately 118,000 registered voters cast ballots.

Tejada, 45, a consultant who has worked on local volunteer committees and served as an assistant to Rep James P. Moran (D-Va.), will take office after he is sworn in this week. He joins Fairfax County School Board Chairman Isis Castro (Mount Vernon) as the only Latino elected officials in Virginia, according to state records.

"This is a historic night not only for the Latino community, but all of Arlington," Tejada said last night at Cecilia's Restaurant, where his campaign team held a victory party. "This is a tremendous step for inclusiveness in Virginia."

Although Arlington is largely Democratic, the special election campaign was closely fought until the end, county officials and political observers said. During the race, both candidates insisted that their platforms represented true change. Clancy, 46, a lawyer who was making his third attempt to win a board seat in 15 months, stressed that Arlington's governing body was in need of an alternative voice because the all-Democratic board had become a "monopoly" soft on development and in favor of too much urban density. Last night, Clancy remained upbeat, saying that local Republicans would not give up trying to gain a seat on the board.

"We'll keep at it until we're able to get a candidate to win," Clancy said. "We just have to keep working hard."

In his campaign, Tejada said he believed strongly in fiscal discipline. He also stressed that he would help open the political process to Latinos and other voices, and he said that funding open-space and the county schools would be his priorities.

Political observers in the county, while impressed with Tejada's campaign, said that the victory was largely a result of the majority Democratic Party organizing itself well and energizing its base around an emotional issue -- Monroe's sudden death at a County Board meeting in January as he presided over his first meeting as chairman.

"Tejada's win really shows the strength of the Democratic Party in Arlington," said Nelson Rios, founder of Virginia Alliance of Latinos Organized for Representation, an Arlington-based nonpartisan group. Referring to the fall elections and races for at least two open Arlington seats in the Virginia House of Delegates, he added, "It also shows what could be ahead in Northern Virginia when it comes to the ability of Latinos to win political office."

In interviews across the county yesterday, many voters considered what kind of change Arlington should embrace. Many said it is important for the board to reflect the county's racial and ethnic diversity. Arlington is 41 percent minority and nearly 19 percent Latino. There have been two blacks on the board in its history -- Monroe and William T. Newman (D), who was elected in 1987 and served until 1993. In addition, some said that the all-Democratic board had managed the county well and that Tejada would be a welcome addition.

"I think our general way of life here is good, and it's been the current leadership that really maintained that," said Pascal Franklin, 32, a business consultant who lives in the Clarendon neighborhood, which has been the focus of much of the county's development over the past decade. "Tejada seems like he would fit right in with what the county has been doing right."

But other voters said that the county could benefit from having GOP representation on the board.

"I don't think we're in bad shape . . . but I'd like to see us do a little better with slowing down some of this development," said Arthur Timlinson, 44, a lawyer who said he voted for Clancy.

Both candidates shared some views. Both said they would vote to reduce the real estate tax rate from the current 99 cents per $100 of assessed value. Clancy said he opposed a baseball stadium in Arlington. Tejada said he, too, was skeptical of the idea and would abide by the views of local neighborhoods.

The campaign captured a good deal of enthusiasm among Arlingtonians. Tejada had raised more than $53,000 by last week -- a record for a county special election. Clancy had raised more than $32,000.

Tejada supporters were convinced that their candidate was in step with the present and future of Arlington politics. Many said Tejada also was the best choice to fulfill Monroe's legacy.

"He has been a champion for so many in the time he has worked and lived in this county," said Inta Malis, a community organizer and Tejada supporter. "He believes in people and what can be achieved in this county."

At Cecilia's Restaurant, J. Walter Tejada is congratulated by Isis Castro, of the Fairfax County School Board.