Chesapeake Energy Corp. CEO Aubrey McClendon has agreed to relinquish his role as chairman of the board, a position he's held since co-founding the natural gas behemoth in 1989 and has used as a springboard to launch the company into Washington energy policy debates. Embroiled in a corporate governance crisis that has placed the Oklahoma City-based gas producer on the credit-watch lists of ratings agencies, Chesapeake announced this morning that McClendon, 52, would step down as chairman when an independent, non-executive chairman is named.