SWAMPSCOTT-After a lot of thought, former Swampscott Selectman Reid Cassidy has decided not to run for state representative in the upcoming special election.?It is with great regret I announce I am unable to run at this time,” he said. “This is a tremendous opportunity and something I really want to do. I would love to take a run for this seat but the timing isn’t right.”Former State Rep. Douglas Petersen, who had been in office for 16 years, stepped down earlier this month when he started his new job as state agriculture commissioner. He represented the 8th Essex District is comprised of Swampscott, Marblehead, and Ward 3, Precinct 4 and Ward 4, Precinct 4 in Lynn.Cassidy, a probation officer in Lynn District Court, said the timing of the special election precludes him from running because of other commitments.?I just can’t do it at this time,” he said. “I am juggling a career, family, law school and studying to take the bar exam in July. It was a family decision that the timing isn’t right. There’s always September or two years from September.”Swampscott Selectman Marc Paster and Marblehead resident Sharon Randall, who both ran unsuccessfully against Petersen in 2004, toyed with the idea of running but decided against it.But even with three potential candidates pulling out there is no shortage of potential candidates to fill out the remainder of Petersen’s unexpired term.Four candidates have already taken out nomination papers and started campaigning, include Democrats Cesar A. Archilla of Swampscott and Lori Ehrlich of Marblehead and Marblehead Republicans John Blaisdell and Tanya DeGenova.Nomination papers are available at the Elections Division of the Secretary’s Office, Room 1705 of the McCormack State Office Building, One Ashburton Place, Boston, and at Lynn City Hall and the Marblehead and Swampscott town halls.Nomination papers for state representative require 150 certified signatures. The deadline for submitting signatures to local registrars of voters for certification is Dec. 26. The deadline for filing certified signatures with the Secretary of the Commonwealth is Jan. 2, 2008.The primary has been scheduled on Feb. 5 and the names of the candidates for the party nomination will appear on the same ballot as presidential candidates on March 4.