The Washington Supreme Court is expected to rule Thursday on a lawsuit challenging the two-thirds majority required for the Legislature to pass a tax increase.

A coalition of lawmakers and education groups sued the state over the issue, and a King County judge decided last spring that the state constitution requires only a simple majority to pass tax proposals. The Supreme Court agreed to expedite its consideration.

The two-thirds majority rule has been approved in a series of initiatives pushed by activist Tim Eyman. Voters most recently approved the supermajority rule last November.