A state Senate candidate from Virginia Beach said he misrepresented his military record, an error that could dim Democrats’ hopes of unseating an entrenched Republican incumbent and winning control of the chamber. Campaign materials for Gary T. McCollum, a cable television executive challenging Sen. Frank W. Wagner (R-Virginia Beach), had said he was “currently a Major in the Army Reserve.” But Army records show he was discharged 14 years ago, in September 2001, according to Ray Gall, a spokesman for the U.S. Army Human Resources Command in Fort Knox, Ky.