Sagadahoc County residents are gearing up for a special election. Residents of Sagadahoc County and the town of Dresden in Lincoln County will cast tallies Tuesday to determine who’ll fill the Senate seat vacated by Seth Goodall, who resigned to serve as New England chief of the Small Business Administration. There are three candidates on the ballot: Republican Paula Benoit of Phippsburg, Democrat Eloise Vitelli of Arrowsic and Green Independent Daniel Stromgren of Topsham. The race is considered a tossup. The GOP traditionally has been strong in Sagadahoc County, with Goodall winning the last election over Benoit by just 162 votes.