Even though Democrats won several House of Delegates races in the Washington suburbs Tuesday, their victories are not likely to alter the temperament of the GOP-controlled legislature when it convenes in January, Republican leaders and political observers said. Four of the new legislators will replace moderate Republicans or other Democrats.

In all, House Democrats picked up one seat, bringing their membership to 39. In the successful Northern Virginia races, David Poisson defeated incumbent Richard H. Black (R) in Loudoun County, and David L. Englin defeated Christopher J.T. Gregerson (R) in Alexandria. In Fairfax County, David L. Bulova defeated John Mason (R) and Libertarian Scott McPherson; Dave W. Marsden defeated Michael J. Golden (R); and C. Chuck Caputo defeated Chris S. Craddock (R) and Charles Eby (L).

"We're very pleased with our candidates," said Del. Brian J. Moran (D-Alexandria), chairman of the House Democratic Caucus. He added that 2005 marked the first time in more than 60 years that the party picked up seats in two successive elections. "Whether it was upsetting an incumbent or taking open seats, [Democrats'] messages resonated," he said.

Although Republicans were concerned about their losses in the Washington suburbs, they said they were relieved to have withstood several well-funded challenges in the region. Prince William County Dels. Jeffrey M. Frederick, Michele B. McQuigg and Robert G. Marshall all survived challenges from Democrats, as did Fairfax Del. Dave B. Albo.

"We still have a strong majority," said G. Paul Nardo, chief aide to House Speaker William J. Howell (R-Stafford). Republicans offset their losses in Northern Virginia by winning an open seat left by Alfred C. Pollard Jr. (D-Lancaster) and defeating Del. B.W. "Benny" Keister (D-Pulaski).

Depending on the outcome of a planned recount in a Richmond House district -- where independent Katherine Waddell challenged GOP Del. Bradley P. Marrs -- Republicans will begin next year's session with 58 or 59 members.

The impact of the Democratic victories in Northern Virginia will be immediately felt in the Loudoun district won by Poisson. The Democrat, a supporter of abortion rights and legal benefits for same-sex couples, will be replacing one of the General Assembly's most socially conservative members.

Black has long had a strong following but also sharp opposition in the General Assembly -- and has been a vociferous opponent of tax increases. Poisson has said that he will focus on bread-and-butter issues and avoid getting distracted by social issues.

"Many of the people who are new to our district are primarily concerned about public schools and the time they spend in traffic," Poisson told reporters in a conference call yesterday. During the campaign he argued that Black was ineffective because he focused on social issues at the expense of pocketbook issues.

Several politicians and political observers said that Black's staunchly conservative message might have turned off newer and younger families in the rapidly changing district and that Poisson ran an effective campaign that highlighted the everyday concerns of voters.

"Dick Black was one of the 'no tax increases ever, no way, no how' politicians," said Del. Joe T. May (R-Loudoun), who represents a district next to Black's. "I don't think that worked particularly well with the new people in this district."

But even though Democrats, aided by late fundraising drives, won two other districts once held by Republicans, most of the new lawmakers are replacing legislators who generally shared their political philosophy on social and fiscal matters.

For instance, Marsden, who will replace a moderate Republican, Del. James H. Dillard II, is close to the former delegate on fiscal and social issues. Marsden, who served as acting director of the department of juvenile justice for a year in 2001, said he wants to focus on stemming rising gang violence in Fairfax and solving the region's transportation problems. During the race, Marsden the Democrat was endorsed by Dillard the Republican.

"People want a moderate, bipartisan government, that's the message that I take from these victories," Marsden said yesterday.

Meanwhile, Bulova has promised to maintain the independent streak of his predecessor, Del. J. Chapman Petersen, also a Democrat. He said yesterday that his priority will be to work on legislation that gives localities the power to better link road construction and other infrastructure improvements to residential development -- also a goal of Gov.-elect Timothy M. Kaine (D).

In Alexandria, Englin, who is replacing retiring Del. Marian Van Landingham (D), has said that he was the logical heir to her legacy and that he will continue her representation of the city. He supports the plan to increase financing for prekindergarten programs espoused by Kaine. He also argues that the state should opt out of the federal No Child Left Behind Act.

Democrat Caputo, who was endorsed by former GOP Del. Gary A. Reese during the race, shares Reese's focus on public school funding, and was supportive of the tax package from last year that raised $1.5 billion for education, health care and public safety.

"Gary and I believed that education was a top priority," Caputo said.