melted alternator plug
 

I got woken up today by my wife telling me that my truck is smoking. I didn't drive it in the past 2 days. I go outside and there is smoke coming out from under the hood. I got the alternator plug out and its half melted to nothing. The part that melted is the plug between the red and white line. Any idea what would cause this to happen spontaneously like that? It was recently hit (not too hard) on the passenger front which broke out the turn signal and corner marker lights including the socket for the turn signal light.