Three losing Republican candidates for the State Senate were the biggest spenders in what observers say were the costliest legislative races in Northern Virginian history.

According to campaign spending reports, the top spender was Herndon Mayor Thomas D. Rust, who spent $41,478 in his campaign for the 33rd District Senate seat. That was almost four times the $11,433 spent by his opponent, incumbent Democrat Charles L. Waddell, who won with 53 percent of the vote and will continue to represent the district spanning Loudoun and western Fairfax counties.

The GOP went all-out to capture the Waddell seat, with Rust collecting $3,000 in contributions from the Republican National Committee, $3,750 from the state party's campaign fund and $750 from the Washington-based GOPAC, another Republican offshoot. Rust was billed more than $15,000 by North American Marketing Corp. of Richmond, a political consulting firm operated by William A. Royall Jr., the GOP strategist who masterminded Gov. John N. Dalton's victory two years ago.

"It's becoming ridiculous," said Waddell, a liberal who has served two Senate terms. "I knew I was on their hit list, but that's a lot of money to spend for a job that pays $8,000 a year." Actually, the annual salary is $5,475.

Just behind Rust in total expenditures were fellow Fairfax County Republican candidates for the Senate James R. Tate, who spent $37,680, and John B. Watkins, who reported $33,200.

Tate lost to Democrat Richard L. Saslaw by 53 percent to 47, while Watkins lost to incumbent Democratic Sen. Joseph V. Gartlan Jr. by 56 percent to 44. The Democrats spent about $20,000 apiece.

"Those totals are much, much higher that I've ever seen before," said M. C. Rappleyea, secretary of the Fairfax County Electoral Board. "It varies, of course, by candidate, but some of the figures seemed shocking when compared to what people were spending four years ago."

The biggest legislative spender among Democrats was Fairfax County incumbent Sen. Adelard L. Brault, who faced a tough challenge from conservative Republican John M. Thoburn. Brault reported raising $35,009 and spending $28,914 in defeating Thoburn by 56 percent to 44. Thoburn raised $13,436 and reported spending $20,226.

Among candidated for the state House of Delegates, the biggest reported spender was Democrat Dean E. Brundage, who listed $30,579 in expenditures but raised only $5,954. Brundage, who finished ninth in a field of 10 candidated for five seats in a district covering northern Fairfax County, Fairfax City and Falls Church, lent himself nearly $26,000.

After Brundage, the three biggest spenders were Republican Del. Martin H. Perper, John S. Buckley and John H. Rust Jr., each of who spent between $20,000 and $25,000 in winning Fairfax-Falls Church House seats.

Buckley, 26, the youngest winner and a staunch conservative, received what appeared to be the largest single contribution, a $5,828 donation of work done by Richard A. Viguerie of Falls Church, the direct-mail wizard who has championed a number of right-wind candidates and causes.

In local races, Fairfax County Board of Supervisors Chairman John F. Herrity (R) was outspent by Demorcratic opponent Vivian E. Watts $37,334 to $34,005. Herrity defeated Watts by 56 percent of the vote to 44.

Republican-backed Arlington County Board incumbents Dorothy T. Grotos and Walter L. Frankland Jr. reported spending $24,251 in their joint campaign, defeating Democratic-backed Mary M. Whipple and Charles W. Rinker Jr., who spen $31,143. Grotos and Frankland reported several major contributions from hotel and real-estate interests, including $1,000 from the Marriott Corp. and $1,000 from Stouffer Hotels of Arlington.

ASPAC, a group working out of the offices of the Northern Virginia Builders Association, made a $1,000 contribution to GOP Fairfax supervisor candidate D. Patick Mullins during the last week of his losing campaign to defeat Democratic Supervisor Audrey C. Moore of Annandale, the board's most outspoken foe of rapid development.

Mullins reported spending $13,851 to Moore's $7,350 but was easily defeated by Moore, who received 65 percent of the vote.