THE BELMONT AVENUE SOCIAL CLUB, Pyewacket, at Center Theater Ensemble. Bruce Graham’s two-act drama about backroom political deals tries very hard to matter. In an unnamed east-coast town, shadowy deal maker Fran Barelli–leader of the Belmont Avenue Social Club–must appoint a successor to corrupt councilman Petey, who’s just died. Barelli brushes aside overzealous young social worker Doug Reardon, whom he’s trained in politics since childhood, in favor of aging lapdog Tommy Krueger; Reardon then takes it upon himself to unearth Krueger’s dirty past, “for his own good.” The ensuing tug-of-war between party loyalty and personal ambition is the stuff of a great David Mamet play. But because Graham spends an entire act touching up his character portraits, he discovers the high stakes only in his play’s final 20 minutes–which are terrific. He’s too fond of expository digressions to crank out a hard-nosed plot, which is what a play like this desperately needs.