CHICAGO — The road to Midwestern acceptance of same-sex marriage runs through Illinois, the home of President Obama that is poised to be the 10th state and the first Legislature in the region to endorse such unions.

In a few short years, attitudes about same-sex marriage are changing in the industrial Midwest. Iowa voters ousted three Supreme Court justices in 2010 who backed a unanimous ruling supporting gay marriage a year earlier. However, last November a fourth judge who was part of that decision survived a recall effort. In Minnesota, voters rejected a constitutional amendment that would have limited marriage to a man and a woman.