The Arlingtonians for a Better County gave its endorsement unanimously last night to the independent candidacy of Ellen M. Bozman for a fourth four-year term on the County Board.

Richard J. Herbst, a federal employe who also is running as an independent, withdrew his bid for the endorsement after failing to get a change in the ABC's rules that would have required him to support last night's winner. Herbst is expected to seek the Republican Party's endorsement at its May 11 canvass, a version of a local primary.

Bozman's victory was virtually a foregone conclusion, since her political roots are with the ABC, a self-described nonpartisan organization with a record of endorsing candidates who also run with the endorsement or nomination of the Arlington Democratic Party.

ABC endorses, rather than nominates, candidates because most of its members are federal employes who are barred by the Hatch Act from participating in party politics. Bozman, a one-time federal budget official, is expected to seek the endorsement of Arlington Democrats at their May 13 mass meeting.

Herbst, addressing the 130 ABC members meeting at Washington-Lee High School, said he came to the convention to call attention to the "plight of federal employes" caused by the Hatch Act restrictions. He criticized the "loyalty oath" rule for forcing members to support the convention's choice, thereby prohibiting them from supporting other nonpartisan candidates.

Addressing the convention, Bozman said her future goals are to continue the stabilization of neighborhoods surrounded by new development, mobilize new residents and technology, maintain fiscal prudence, improve the environment and improve community programs, especially for the frail elderly, immigrants and children.