PHOENIX - The U.S. Supreme Court derailed a key part of Arizona's campaign-financing system 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 might 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. The court "could have let that sit until that race is over."

The court's brief order may have the greatest effect on the GOP gubernatorial primary, in which Gov. Jan Brewer, who is running with public financing, is being challenged by Buz Mills, a millionaire businessman largely using his own money in his first bid for office.

Under Arizona's system, candidates who opt for public financing can get matching funds up to two times their base amount when they are outspent by privately funded rivals or targeted by independent groups' spending.

Critics say the funds chill the free-speech rights of privately financed candidates and their contributors by inhibiting fund-raising and spending.

State officials and advocates of public campaign-finance systems say the matching funds help combat contributions-for-favors corruption and encourage more people to run for office.

Lower courts that considered Arizona's matching funds split on their constitutionality.

Nearly half the candidates for state office who qualified to run in the primary were running with public funding.

At least two other states, Connecticut and Maine, have similar provisions, but Tuesday's Supreme Court order affects only Arizona.