How to handle a client you're not comfortable with

I'm in an entry level position at a PR firm and we handle a variety of different clients. We could possibly take on a new client and I know I would be the one working on the account.  What the client is involved with  I do not feel comfortable being part of because of ethics(goes against my principles/ values). How would you say to handle this, should I bite the bullet and get the job done or should I say something to my senior adviser?

If you believe something isn't right or you're being asked to do work that is against your values or is unethical by nature, raise the flag to your boss. Have a 1:1 with your senior adviser (assuming this is your boss at the firm?) and give him or her the specifics of what's going on. You two can come up with a game plan on how to address it with the client or another path forward. If the issue with the client is more of a personal preference of yours, you might be switched off the account or asked to get over whatever the issue is and do the work, so be prepared for that. 

Hope this helps! Keep us posted.