Three candidates for the Arlington County Board will be on the ballot for the Republican Party's "canvass" -- a party-run primary -- Aug. 18.

Although the canvass is designed to select a GOP nominee for the County Board election this fall, two candidates -- Jim M. Wright and Roger S. Morton -- will be seeking a party endorsement only, since both are federal employes and barred by the Hatch Act from participating in partisan politics. If either wins the canvass, each has said he plans to run as an independent, with party backing, which would meet the nonpartisan requirements of the Hatch Act.

The third candidate, retired Air Force Col. Robert E. Harrington, says he will run as a Republican if he wins the canvass.

The canvass, where Republicans will select one candidate for the general election Nov. 3, i scheduled for from 3 to 8:15 p.m. at the Lyon Village Community House at Lee Highway and North Highland Street in Arlington. The canvass is open to any registered county voter who expresses support of GOP principles and who pledges to support the choice of the canvass. The filing deadline for the canvass is 8 o'clock tonight, although county GOP leaders say they expect only the three candidates who already have declared.

All three candidates in the GOP race are hoping for a spot on the general election ballot against incumbent Board Member Ellen M. Bozman, who is seeking a third four-year term. Bozman, who is running as an independent, already has won the endorsement of county Democrats and the nonpartisan Arlingtonians for a Better County.

Two of the three candidates already have won the backing of incumbent county board members.

County Board Member Walter L. Frankland, a Republican-backed member of the board, has endorsed Harrington, who retired from the Air Force in 1972 after 30 years of service.

At the same time, Board Chairman Stephen H. Detwiler, also a Republican-backed member, has given his support to Wright, a planner with the U.S. Treasury Department.

Harrington, who worked as business manager of St. Agnes Episcopal Girls School in Alexandria from 1972 until he resigned in June to work on his campaign, has lived in Arlington for 23 years. He is a member of the county Civil Service Commission and the ad hoc committee on improving county government. A major theme of his campaign, Harrington said, will be the efficiency of government.

"The time is overdue for the county government to look into some of its programs and see if they are doing what they're supposed to do and if they're cost-effective," he said.

Harrington said he also supports economic development in Arlington and believes the county should derive some benefit from growth around the Metro stops.

Wright, one of two federal workers in the GOP race, has lived in Arlington eight years and is a member of the Committee of 100, a civic organization active in studying county affairs. He also is a member of the county energy conservation committee and former chairman of the county ad hoc housing advisory committee.

"I'm running because I think the county needs the expertise of an urban planner on the board in light of increasing development, particularly at Metro stops," said Wright, who in addition to his planning position at Treasury was once a development planner for the U.S. Department of Housing and Urban Development. "I believe I can do a good job in ensuring that Arlington will continue to have quality development that will lead to a livable environment -- not just office buildings."

Wright said he is also concerned about government efficiency and economic development that will help reduce county real estate taxes.

Morton, the third candidate in the GOP race, has lived in Arlington 10 years and works in communications for the U.S. Defense Department. Morton unsuccessfully sought appointment to the county school board last year. He serves on the county's fiscal affairs advisory committee and its cable television advisory committee and is a member of the Highland Park-Overlee Knolls civic association.

Like the two other GOP candidates, Morton said he is particularly concerned about financial stability in the county.

Noting that the real estate tax rate dropped from $1.49 for each $100 of assessed valuation to 96 cents during the past three years when he was a fiscal adviser, Morton said, "I think I could do a good job on the board. I've served the county in the last three years on both the school and county sides of fiscal matters.

"And if the trend of reducing real estate tax rates is to be continued, it's going to require even more fine tuning of the budget."