Don't wear anything with OBAMA or McCain to the Voting Polls!!!! - It's the Law

This not completely true it depends on the state you live in  and what their laws are on passive electioneering.  Here are two good pages that address this issue:

http://www.snopes.com/politics/ballot/electioneering.asp  - This one is for GENERAL PURPOSES.

http://www.dailykos.com/story/2008/9/24/105716/347/604/608597 - This has to do more with the state of Maryland.

I think the best bet is to NOT WEAR OBAMA OR MCCAIN paraphernalia and to be informed of the law in your state.