Contacting Potential Advisor After Being Waitlisted for PhD Admissions I applied to a few PhD programs in the US (engineering, fall 2017), but didn't contact any potential advisers before (huge mistake, I know, but somehow I got accepted into a few of them anyways).

However, I was waitlisted for the program I wanted the most. 

So, I would like to know if it would be wise to get in touch with my potential adviser now, and tell him about my research background and ask if he would be willing to advise me. I'm a little afraid that this might be seen as rude or unpleasant..

This may be a bit personal, but I'm sure there are a lot of experienced people in this group who might have been through this same situation before... Any hint would be extremely helpful right now...

Thank you!
You could but it's likely too late. The order of waitlist rolldowns is usually determined at the admissions meeting, sent to the graduate school, and is now beyond the professor's (and occasionally the department's) control. 

Departments and universities do vary in practice. There's nothing to be lost in emailing the professor but don't assume a response. No news would be bad news.