For a generation, the cordial, bushy-browed Virginia Sen. Clive L. DuVal 2nd, son of Yale and Yale Law School, seemed a perfect match for his constituents in the prosperous Northern Virginia communities that hug the banks of the Potomac River.

Like many of the residents of McLean, Langley, Great Falls, north Arlington, Falls Church and Vienna, DuVal was upright and well-heeled, a land owner with a certain standing in society and a respect for the status quo.

Reelected time after time to the House of Delegates and later to the state Senate, DuVal, a Democrat in a legislature dominated by Democrats, rose to become the dean of Northern Virginia's 29-member delegation to the General Assembly and chairman of the policy-making Democratic Caucus. His quadrennial election campaigns resembled coronations: Even when a Republican bothered to oppose him, DuVal would trounce his foe easily. It was all rather predictable and familiar.

Until this year.

After 22 years in office, the 75-year-old DuVal is in the reelection fight of his life. Bobbie G. Kilberg, a 42-year-old former White House associate counsel in the Ford administration, is matching DuVal blow for blow, dollar for dollar -- even resume for resume.

A moderate Republican in a district that tends to vote Republican in congressional and presidential races, Kilberg is exactly the sort of articulate, poised challenger that GOP leaders have been hoping would surface to take on DuVal, who says this is likely has last campaign before retirement.

Kilberg and DuVal are locked in what is by far the most expensive -- and, most analysts agree, the most erudite -- state legislative race in Northern Virginia. By Election Day Nov. 3, each candidate expects to have raised about $150,000.

Both DuVal and Kilberg are Ivy League-educated Yale Law School graduates with an array of academic achievements. Both came to Washington to work for Republican administrations (Kilberg for Nixon; Duval for Eisenhower), then stayed, moving into private law practice, community activism and, finally, state politics.

The result is what most analysts acknowledge is a rare spectacle in state politics: a race, focused on the issues, between candidates who are widely respected for their experience, intelligence and commitment.

"It's not your usual state Senate race," said James S. Turpin Jr., a Republican campaign consultant to Kilberg. "You've got two very qualified candidates, two candidates who are very well educated and experienced and knowledgeable . . . . "

Kilberg, who acknowledges that she is trailing DuVal in the polls, has attacked the senior senator for what she terms his record of "going along to get along" in the legislature. For too long, she declares in speeches, Northern Virginia has failed to collect its "fair share" of transportation financing and other revenue from the state because of the region's malleable lawmakers.

DuVal -- as well as many of his fellow lawmakers -- points out that in the General Assembly, which functions according to a system of seniority, Northern Virginia would lose influence if it replaced a veteran Democratic senator with a freshman Republican. What's more, he says, as a Republican in a legislative body dominated by Democrats, Kilberg would have last dibs in committee assignments -- a key to collecting chits in the Senate.

DuVal, a former Republican who switched parties in 1960, said: "It took me 10 years to get a seat on the Senate Finance Committee," the powerful panel that appropriates funds for state programs from road-building to university professors. "It would probably take Bobbie at least as long -- if she ever got a seat." The 15-member Senate finance committee currently has just one Republican member.

As for Kilberg's insistence that she is going to shake up the system and wring more financing and concessions from downstate lawmakers for Northern Virginia, DuVal is skeptical. "You simply can't come in there and push your way to the front. You won't have the committee assignment or the understanding and regard of your colleagues who will be watching you closely."

Responds Kilberg: "It's not inconsistent to be able to work effectively with {other senators} and at the same time to aggressively represent constituents. I understand what give-and-take is all about . . . but that atmosphere can be opened up in a positive way. We need a change."

Many analysts believe that DuVal is in a strong position to win a fifth four-year term because Northern Virginia has enjoyed a string of legislative victories in recent years.

After years of suffering under a road financing allocation that favored rural areas at the expense of more populous regions, Northern Virginia scored a major victory in having the formula changed in 1985. Since then, the region also has benefited from Democratic Gov. Gerald L. Baliles' initiative to vastly increase the amount of road construction financing for the state.

Kilberg argues that it took too long for those advances to be made, and that even now, they are too little, too late. She has embraced a number of transportation proposals -- most of which DuVal also has endorsed -- including rapid rail service to Dulles International Airport and the privately financed extension of the Dulles Toll Road to Leesburg.

Kilberg, who is seven months' pregnant, has stressed the need for better child-care programs -- a priority that Baliles has emphasized. She also has pledged to press for a rehaul of the admissions policy of state universities, particularly the University of Virginia, which would reduce the number of out-of-state students to make room for more students from Northern Virginia.

DuVal, pointing out that about 40 percent of U-Va.'s in-state undergraduates are from Northern Virginia, is opposed to such a change.