Arlington County Board Chairman Stephen H. Detwiler, who cast the decisive vote this spring to increase the county property tax rate, has ordered a budget analysis that could lead to a tax cut one month before the Nov. 2 general election.

Detwiler, a Republican, is seeking reelection to the board, and Democratic board members charge that Detwiler is playing election-year politics.

"He's treating the tax rate as a political yo-yo, up and down and down and up, in his reelection year," said Democratic board member John G. Milliken.

Detwiler said the analysis, to be done by county staff and expected in time for an August board meeting, is not politically motivated but simply fulfills a promise he made this spring to seek a mid-year review of the county budget.

"The budget is a set of projections as to what is estimated to occur in the future," Detwiler said. "Therefore, by its very nature, the numbers cannot be absolutely accurate."

In a prepared statement, he said he hoped the analysis would allow a 2-cent cut in the real estate tax for the October collection, to 96 cents per $100 of assessed value, or a 4-cent cut to 94 cents.

During budget deliberations in March, Detwiler sided with the board's two Democrats in a surprising 3-2 vote for a 2-cent increase in the property tax rate, to 98 cents. His vote angered some of his conservative supporters, said Lois J. Thomas, Detwiler's staff assistant.

County Board members have divided along partisan lines over the reason for Detwiler's analysis request. "He's doing what he said he would do (this spring)," Republican board member Dorothy T. Grotos said.

But board member Ellen M. Bozman said: "The timing is one thing that makes it political."

Detwiler defended his request, saying he expects new financial figures that may allow a tax decrease.

"I have no information available to me at this time that indicates that a reduction in taxes is possible," he said. "However, I firmly believe that we will find significant changes in the revenue and expenditures from what they were in the spring which may possibly allow for some reduction."

Democratic candidate Mary Margaret Whipple, who is running against Detwiler, strongly disagreed. "There would be very little new information since the budget was completed two months ago that would make the budget very much more accurate," Whipple said. "He is talking about revising revenue projections for a fiscal year that is just beginning (July 1)."

"It seems to me to be a blatant political move that is unprecedented in Arlington County," she said.

Detwiler disagrees.

"I wonder if Mrs. Whipple would make the same accusation with regard to the time that the Democrats reduced the tax rate from the second payment in 1977, just prior to Mrs. Bozman's reelection," he said.

Bozman said the 1977 change came at a time when the County Board, as part of the normal budget process, usually set the tax rate to take effect for the October collection. The board now sets the rate earlier in the year, she said.