In the wake of Joseph S. Wholey's decision not to seek a third four-year term on the Arlington County Board, local politicians are gearing up for what all predict will be one of most hotly contested races in Arlington in recent years.

At stake in the November elections is political control of the five-member board. Wholey's departure leaves two incumbents supported by Republicans and two incumbents backed by the combined forces of the Democratic Party and the nonpartisan Arlingtonians for a Better County (ABC). Wholey is a member of the ABC coalition.

Control of the board has been a hot issue since the 1975 election of Republican-endorsed candidates Dorothy T. Grotos and Walter L. Frankland Jr. Since them, however, other Republican-endorsed challengers have been handily defeated by incumbents John W. Purdy and Ellen M. Bozman, who, like Wholey, have been endorsed by the ABC coalition.

This year with Wholey (who was regarded by members of both parties as virtually unbeatable) out of the race, the Republicans are hoping to wrest majority control from the Democrats. Republican-endorsed board members last held a majority on the board in 1969.

"This is a critical year," said Allen H. Kitchens, former ABC chairman and one of three candidates likely to seek the combined endorsement of the ABC and the Democratic Party at their April conventions. "There's a tremendous concern about holding the majority this year."

"The prospects of running a candidate against Joe Wholey were difficult to say the least," said Pete Teeley, chairman of the Arlington County Republican Party. "But now we have a very strong chance to capture that seat. I can think of two or three likely candidates, none of whom have run before."

Teeley declined to name any of those possible candidates because, he said, he hadn't consulted them yet.

But two men mentioned by other party leaders as possible candidates squelched speculation that they might run.

"There are probably one or two idiots out there saying I might run," said an amused Steve Detwiler, mentioned by several party leaders as one of the county's most promising young Republicans, "I would not run."

Republican-endorsed independent Sherman Pratt, defeated last year in his bid for Bozman's seat said, "My name may have been mentioned, but I've given it no encouragement. I do not plan to run again."

Other names mentioned by local Republican leaders are Fred Burroughs, a member of the Economic Development Commission; Richard Titus, unsuccessful school board candidate, and Hal Ekern, who ran unsuccessfully last year for a seat in the General Assembly.

The three people mentioned most often as likely to seek the combined ABC-Democratic endorsement at the conventions to be held in late April are Kitchens, Joe Pelton and Marianne Karydes. All three acknowledge that they are "very seriously considering" running for Wholey's seat.

Pelton is past president of the Arlington Civic Federation, and Karydes is vice-chairman of the Arlington Democratic Party.

Kitchens, Pelton and Karydes apparently are regarded as equally strong candidates. "I don't think there's any reason to think that anyone has a leg up," said county board chairman John W. Purdy.

But several observers noted that among Pelton's strengths is his South Arlington address. For several years, South Arlington residents have complained that the board - composed exclusively of North Arlingtonians - is unsympathetic to their problems.

Despite Republican hopes of an upset, the departure of the fiscally conservative Wholey, respected by his conservative, Republican-backed colleagues for his willingness to vote with them on budget issues, was greeted with restraint.

"If the Republicans are unable to beat (the ABC-Democratic) candidate, the county will be worse off because of Wholey stepping down," Frankland said.