porter

For my 1998 Maxima. For the past few months, I have noticed that my Pasenger-side rear floor mat keeps getting wet (other 3 mats are fine). I do not think it is due to rain since it hasn't rained since I last checked that the mat was dry (so prob not a hole in floorboard). I know that most car A/C systems have a condesent drin tube that leads to the ground and that if it gets clogged, it will back up and get the carpets wet. My front mats are dry though! Any thoughts?
Porter