A federal judge has declined to dismiss a lawsuit over Michigan's ban on straight-party voting.

The decision Friday means Judge Gershwin Drain will hold a trial on whether the law violates the rights of black voters, who typically vote Democratic. The decision wasn't a big surprise: The same judge expressed concern and suspended the ban before the 2016 election.

Straight-party voting means making a single mark on a ballot to pick candidates of one party. Republicans, including Gov. Rick Snyder, say the ban will inspire voters to do their homework instead of simply choosing a party.

Nearly 50 percent of all Michigan ballots were straight-party during the 2016 election. It was popular in Republican-friendly counties won by President Donald Trump, such as Ottawa, Allegan, Livingston and Kent.