Two more Democrats enter race to succeed longtime Boston mayor By Scott Malone BOSTON (Reuters) - Two Democrats jumped into the race to succeed Boston's longest-serving mayor on Tuesday, the first to declare their interest in succeeding Thomas Menino since he told the city last week that he would not run for an unprecedented sixth term. State Representative Martin Walsh and City Councilor Felix Arroyo said on Tuesday they were interested in the seat, joining Councilor John Connolly, a former school teacher who began his campaign in February, the one candidate to do so before Menino said he would leave office. "I've made my mind up," Walsh, who has served in the statehouse since 1997, told the Boston Herald. I'm running for mayor. Walsh did not immediately return a call seeking comment. Arroyo told supporters in a fundraising letter sent on Tuesday, "I am seriously considering running for mayor of Boston." Incumbent mayors are rarely unseated in Boston, Menino got the job in July 1993 when his predecessor was made U.S. ambassador to the Vatican, and observers expect a large number of candidates to enter the race. Candidates have until May 13 to officially declare their interest and will face an open September 24 primary, with the two top vote-getters facing off in the November 5 general election. Boston voters face a busier-than-usual election season this year, with five candidates currently vying for the U.S. Senate seat previously held by Secretary of State John Kerry. In that race, voters will pick a Democratic and a Republican candidate on April 30, with a special election to follow on June 25. Early polls have shown U.S. Representative Edward Markey with a leading position among Democrats and former U.S. Attorney Michael Sullivan leading among Republicans. The No. 2 Democrat in the field, U.S. Representative Stephen Lynch, late last week batted away questions that he would drop out to run for mayor, saying he remained focused on the Senate contest. Reporting by Scott Malone; Editing by Cynthia Johnston and Grant McCool