Sorry, but on a resume I think that is a acceptable usage by Obama. When your boss says that you “served as a cigarette smoker” you can damn well put “Cigarette Smoker” as your official title.
Not exactly, for example, if your title is Customer Service Rep but you helped train a new hire class once, your title didn’t evolve to Trainer, you are still a Customer Service Rep. (this came up on a resume I saw recently)
This is really not significant — more semantics than anything else. The term “professor” is in widespread usage to mean anyone who is teaching a course at a post-secondary institution. Students routinely address and refer to people whose official titles are “Lecturer” or “Instructor”, as “professor”. The popular website RateMyProfessor.com is understood by everyone to cover all people who teach college courses, regardless of their formal titles. This informal usage is so pervasive that the University of Chicago even used it in this written press release.
It wasn’t on a resume, just some campaign literature. A formal resume should carry formal titles of all paid positions held, and his formal title for this position was presumably “Lecturer” or some other term not containing the word “professor”. If he’d put on an actual resume that he was a “Professor” at the law school, I’d have a big problem with that, but for campaign materials there’s nothing wrong with use terms as they are normally used in informal speech and writing.