Washington (CNN) -- Politically polarized Wisconsin is next up in the traveling legal battle over whether requiring photo identification to vote discriminates against minorities and disabled people.
Critics of mandatory government-issued photo IDs say minorities are disenfranchised by the requirement. The lawsuit says the state constitution declares the only ineligible voters are felons, children and the mentally incompetent. The case was brought in Madison against Gov. Scott Walker and state election officials by the ACLU.
Supporters of the law, written and passed by Republicans, say the singular purpose is to combat voter fraud at polling stations.
Fifteen states require photo IDs to vote. Another 16 states require IDs but do not require photos, according to civil rights officials.
In 2008, the Supreme Court upheld an Indiana law that requires photo IDs.
At a commemoration of the Rev. Martin Luther King Jr. on Monday in the Wisconsin state capitol rotunda, the audience cheered a keynote speaker who said King would not have approved of a state law that required a photo ID to vote, according to officials who attended.
The case will be heard by Dane County Circuit Court Judge Richard Niess in Madison on Thursday.
The Justice Department Civil Rights Division said Tuesday it expects to announce its decision on approval of the Mississippi photo ID law on March 5, and on the Texas photo ID law on March 12. Both states must have their voting changes cleared by the Justice Department under the Voting Rights Act.