defection (
http://definr.com/defection)
n 1: withdrawing support or help despite allegiance or
responsibility; "his abandonment of his wife and
children left them penniless" [syn:
desertion,
abandonment]
2: the state of having rejected your religious beliefs or your
political party or a cause (often in favor of opposing
beliefs or causes) [syn:
apostasy,
renunciation]