A celebrtity who gets political. In some extreme cases (like the guy who is now governor of california) they will run for office and win. But if one just makes public political statements and/or supports a candidate, then that celebrity has become a celebricrat.
Naturaly, most celebricrats are on the political left (celiberals) because that is the less moralistic party, the strongest party in California, as opposed to the right-wing celebrities (constarvatives). The celiberals are often denounced by right-wing pundits as traitors. The constarvatives are usually just blown off by left-wingers as rich morons.