1) n. A person who was a celebrity and then got involved in politics. Is observed by the public and media mainly for being a celebrity rather than a politician.
2) n. A politician who became famous for a position or action and is now only a celebrity because of the former position or action, no matter how menial their current position is or even though they're retired from politics.
1) Arnold Schwarzenegger is a political celebrity.
2) Colin Powell is a political celebrity.