Lawyers for Arizona's governor are trying to head off a challenge from fellow Republicans in the state Legislature who are opposed to a new law expanding Medicaid.
A court hearing in Phoenix on Friday will test Gov. Jan Brewer's contention that the lawmakers challenging the law don't have the right to sue.
The GOP lawmakers argue that the law passed in June that expands the state's health insurance plan for the poor violates the state Constitution because it raises taxes without a required two-thirds vote.
Brewer passed the law by putting together a coalition of Democrats and some Republicans who supported the expansion. She argued that a hospital assessment designed to pay the state's costs isn't a tax.
The suit was filed by the conservative Goldwater Institute on behalf of 36 Republican legislators.