Michigan had the nation's costliest state court races in the 2010 election cycle, with most of the money coming from outside groups that paid for a flurry of negative campaign ads, according to a report released Thursday by a judicial watchdog group.The Michigan Supreme Court race accounted for a quarter of the $38.4 million spent nationally in 2009-10, according to the report prepared by the Justice at Stake Campaign, the Brennan Center for Justice at New York University School of Law and the National Institute of Money in State Politics.Because Michigan doesn't require outside groups to disclose what they're spending on TV ads, the court race could have cost as much as $11.1 million, it said.