WASHINGTON — Attorney General Richard Blumenthal of Connecticut sat down with a reporter for a local news outlet this week in an effort to move beyond an issue that has bedeviled his Senate campaign: his claims about his military service during the Vietnam War. But the interview, with The Connecticut Mirror, a news Web site, raised more questions about that chapter in his life, as Mr. Blumenthal offered a version of events that was sometimes at odds with historians’ accounts of the period. At one point in the interview, Mr. Blumenthal, a Democrat, said he joined the Marine Corps Reserve...