Several dozen people are rallying outside the federal courthouse in Detroit to show their support for overturning Michigan's 2004 constitutional ban on same-sex marriage.
U.S. District Judge Bernard Friedman may throw out the law Wednesday after hearing arguments in his courtroom.
Related story: Gay marriage could be legal in Michigan for short period
It was his suggestion that Detroit-area nurses Jayne Rowse and April DeBoer challenge the ban by amending their 2012 suit challenging a state law that bars same-sex partners from adopting each other's children. The judge's invitation has gay rights supporters believing marriage may become a reality in Michigan.
Related story: Clergy to sign marriage licenses if judge rules for equality
Rowse and DeBoer appeared at the rally. They say that if the judge rules in their favor, they will not immediately apply for a marriage license because they fear the decision could still be overturned on appeal.
Slideshow: State-by-state look at same-sex marriage