Secretary of State William Galvin has opened an investigation into allegations that a large number of East Longmeadow voters had their party affiliations changed without permission. Town officials were notified Friday that Galvin’s office is looking into voter registration fraud for the upcoming Sept. 6 primary. The investigation will determine if a large number of voter registrations “were improperly altered and changed ... in violation of law,” according to Michelle K. Tassinari, director of the office’s election division. “Secretary Galvin considers this a matter of urgent circumstance,” she added. Brian S. McNiff, a spokesman for Galvin, would not say how...