MARBLEHEAD-Some candidates lining up for state Rep. Doug Petersen’s (D-Marblehead) seat are rethinking their position.Swampscott Selectman Marc Paster, who ran unsuccessfully against Petersen in the last election, has decided not to run in a special election for Petersen’s seat, which represents Marblehead, Swampscott and two precincts in Lynn.?It was not an easy decision, but I decided not to run for state representative,” he said. “I started my research by making initial inquiries and phone calls. I met with political consultants and pollsters. I came to the conclusion that the majority of the people that vote in democratic primaries really do not represent my broader base of support.”Petersen is officially stepping down after 17 years as state representative for the 8th Essex District on Nov. 26. to become the state’s new agricultural commissioner.Paster said he crunched the numbers and, when it comes to the Democratic primary, there are twice as many voters in Marblehead as in Lynn and Swampscott combined.?That has always been a Marblehead seat,” he said. “People who vote in the Democratic primary are very active members of the Democratic Town Committees and I don’t think I could win the primary.”A special election has not been called yet, but one candidate already made a formal announcement she is running for Petersen’s seat.Lori Ehrlich of Marblehead officially announced her candidacy last week at the corner of Humphrey Street and Lynn Shore Drive on the Swampscott/Lynn line.Ehrlich, who has a master’s degree in public administration from Harvard’s Kennedy School of Government, is best known as an environmental activist and a founding member of HealthLink, an environmental group based in Salem.Former Swampscott Selectman Reid Cassidy, who is a Democrat, also expressed an interest in running for the seat, but he said he has not made a final decision yet.?I’m still seriously considering it,” he said. “I have feelers out. I’m talking to family, friends and community members. I’m weighing my options.”Cassidy said the timing of the special election would be a crucial factor in his decision.?I am currently finishing law school and preparing to take the bar exam now,” he said. “The timing is a critical factor.”Like Paster, Marblehead resident Sharon Randall ran unsuccessfully against Petersen in the last election. Randall, who is a Republican, was born in Pennsylvania, grew up in Ohio and moved to Stoneham in 1980. She relocated to Marblehead six years ago where she lives with her husband Edward Principe, who is a retired state trooper.?I’m considering running for this seat,” she said. “It’s something I’m very interested in.”