A judge ruled that a nonprofit group must disclose donors who financed more than $200,000 in campaign ads touting public schools chief Tom Luna's education overhaul.
Late Monday, Fourth District Judge Michael Wetherell ruled in favor of Secretary of State Ben Ysursa, who had filed the lawsuit against Education Voters of Idaho.
Wetherell gave the group a deadline of Wednesday.
Earlier in the day, however, Wetherell suggested the case would likely be appealed to the Idaho Supreme Court.
Ysursa argued that voters now headed to the polls will suffer irreparable harm if they can't find out who put up the money for the ads.
Education Voters of Idaho founders Debbie Field and Phil Reberger are trying to conceal the donors, saying federal law protects their identities.
The group declined to comment immediately after Wetherell's ruling became public.