Adding Vice President Bush to her glittering cast of supporters, Virginia state Senate candidate Bobbie Kilberg was feted last night by about 500 Republicans in one of the Washington area's GOP strongholds.

At a cocktail reception on the lawn of the Evans Farm Inn in McLean, Kilberg, a Republican former White House associate counsel who is challenging Democratic Sen. Clive L. DuVal 2d in the Nov. 3 election, was hailed by Bush as "someone who's awfully bright." The vice president offered Kilberg his "wholehearted endorsement."

The race between Kilberg and DuVal in Virginia's 32d District, which includes McLean, Great Falls, Falls Church and north Arlington, is one of Virginia's most expensive and hard-fought races for state Senate this year.

Kilberg, 42, who has wide-ranging legal experience, has raised $98,000, some of it from senior Republican officials such as Deputy Secretary of Defense William H. Taft IV, National Security Adviser Frank C. Carlucci and former Navy secretary John F. Lehman Jr. In addition to Bush, former national security adviser Robert C. McFarlane also attended last night's gala.

DuVal, the dean of Northern Virginia's 29-member legislative delegation to the General Assembly, was first elected to the House of Delegates in 1966 and held the seat until running successfully for the Senate in 1971. DuVal, also a lawyer and one of the most respected members of the General Assembly, has won reelection repeatedly despite running in a heavily Republican district. He has raised about $90,000.

Kilberg launched her race early this year as a political unknown. She waged a tough and expensive primary battle in June against conservative Republican Joyce Sutcliffe, winning by a 3-to-2 ratio and boosting her profile in the district.

In an interview yesterday, Kilberg said she probably still trails DuVal by eight to 10 points, a margin she called "within striking distance." DuVal, who has campaigned hard and has said he is taking her challenge seriously, estimated his lead at closer to 15 to 20 points.

DuVal has kind words for Kilberg -- he called her "very able" in an interview -- but has stressed his own experience and seniority in Richmond. He also points to a string of recent legislative victories for Northern Virginia, including a redistribution of the state's formula for road construction that means more money for the region.

Kilberg also has praised DuVal's personal qualities but has attacked him for supporting a proposal to introduce a lottery to Virginia and for backing measures that would increase taxes for individuals in high-income brackets.

Kilberg, who is six months pregnant, told the crowd last night that she is the only candidate who can offer voters "two-for-one."