PHOENIX — The U.S. Supreme Court derailed a key part of Arizona's campaign financing system on Tuesday, preventing the state from giving extra money to publicly funded candidates facing privately funded rivals and changing the election rules in the thick of primary season. The court stopped Arizona from disbursing so-called matching funds at least until it decides whether to hear the opponents' full appeal. As they await a final ruling that may not come until the fall or even later, candidates and their advisers are reworking their strategies, with publicly funded candidates having to compete with fewer dollars. "This ruling is obviously going to have a direct impact on candidates' strategy," Arizona State University political science professor Patrick Kenney said.