A three-way race for mayor is taking center stage as the city’s 2013 election season gets underway. The deadline for returning nomination papers recently passed. In the mayor’s race, two-term incumbent Scott D. Galvin faces opposition from John P. Flaherty, a local philanthropist, and former state representative Patrick M. Natale. The mayor’s race is one of two that will be featured in a Sept. 17 preliminary election. In the other, Ward 5 Alderwoman Darlene Mercer-Bruen is being challenged by James M. Fletcher Jr. and Paul F. Muise Jr. The top two finishers in each race will proceed to the city election on Nov. 5. Other contested races that will appear on the November ballot feature incumbents Paul J. Denaro and Richard M Haggerty along with Michael P. Concannon competing for two alderman-at-large seats. Ward 1 Alderwoman Rosa DiTucci facing a challenge by Kevin C. Meaney. Ward 3 Alderman Mark E. Gaffney squaring off against former School Committee member Michael Scire. Ward 6 Alderman Michael L. Raymond contending with Francesco S. Recchia. In addition, there are seven candidates for five School Committee seats: incumbents Patricia E. Chisholm, Michael Mulrenan, and John W. Wells; and Ellen Crowley, Joseph E. Demers, Stanley Malvarosa, and Charles Viola. Three aldermen are running unopposed.