OLYMPIA (AP) — The state Supreme Court is scheduled to hear arguments Tuesday on the initiative that requires a two-thirds vote of the Legislature to raise taxes.

A lawsuit was filed in March by Senate Majority Leader Lisa Brown of Spokane. She says the initiative is an unconstitutional check on lawmakers’ power.

Voters approved I-960 last November. It reaffirmed the higher vote threshold for tax increases that were mandated in 1993 by I-601.

Initiative sponsor Tim Eyman says Democrats hope to clear the way to raise taxes in next year’s session.