It's already started. Let's see what that nice Mr. Trump says about it.
"On Monday, the Idaho House of Representatives asked the U.S. Supreme Court to overturn Obergefell v. Hodges, the landmark 2015 case that legalized same-sex marriage nationwide. If the Supreme Court takes up the challenge and rules in favor of the Idaho House, it could mean the end of gay marriage in the United States."
Source: USA Today