George L. Barton, a former newspaper editor, announced Tuesday that he will seek the Republican nomination for at-large chairman of the Loudoun County Board of Supervisors this fall.

Barton, who is president of a public relations firm in the Countryside area of eastern Loudoun, lives in Hamilton, in western Loudoun. He described his candidacy as designed to bring unity to the county government. By editing the Loudoun Times-Mirror newspaper for six years, Barton said, he developed a "true countywide perspective."

The only Republican to enter the race so far, Barton is the best-known Loudoun resident to declare for the new, four-year chairman's post. The position was created by a November 1990 referendum question approved by 83 percent of the voters. The board chairman has been chosen annually by the eight district supervisors from their own ranks.

Chairman Betty W. Tatum (D-Guilford) has not formally announced her intentions for the fall elections. Democrat Frank Hyatt, of Lovettsville, has declared that he will seek his party's nomination for chairman; Hyatt plans to emphasize education and housing.

Independent hopeful Alfred Van Huyck, an advocate of carefully managed growth who lives near Round Hill, was the first candidate to declare for the chairman's post. Supervisor Steve W. Stockman (R-Broad Run) recently announced that he will not run for chairman or his district seat this fall.

Barton said the November referendum on countywide election of the board chairman and the decisive defeat of Supervisor Howard P. Smith (D-Sterling) sent a strong message that the voters want "a different brand of leadership" as well as a different government structure.

Barton served on the Blue Ribbon Committee, which studied Loudoun's form of government and strongly urged at-large election of the board chairman.