An actual elitist is someone who treats anyone who is not as rich/strong/popular as him/her like dirt. A pretentious jerk who has no friends and acts like he's important to make himself feel better.
However, this is also a word sometimes used in politics to marginalize a person who actually knows what they are talking about, uses scientific evidence, or who knows how to lead. Rather than elect someone who is the most qualified to run a country, people would rather vote for the person they see drinking a beer on the news, and as a result countries end up with Presidents like George W. Bush.
Person: I think that this candidate has a good plan to reduce greenhouse gas emissions, he has a lot of scientists backing him up.
Idiot: But is that candidate someone I could have a beer with? I want a candidate who understands the needs of the people.
Person: But shouldn't the people have a leader who cares about real issues and bases their decisions off evidence?
Idiot: Sounds like an elitist to me.