Can you legally use the names of elected officials, living or dead, in a fiction novel?

You can but it is not a good idea.  In fact, editors warn against using the names of real people in books.  It is really not the use of the name, you understand, but it is how you portray the characters and the story line that can get you in to trouble.  It could open you up to libel suits if yu are not careful and that is not something that you need to be involved with. Vioating their names and likenesses or "smearing their good (or bad) names" is a no no.  And even if you made them the hero I still would avoid using their names.  Is it possible to use fictional analogs instead?  Think about it.  It will save you a lot of time and aggravation in the end.  Good luck.