Chief Justice John Roberts preserved one of President Barack Obama's main legacies—and helped forge his own—by largely upholding the president's health-care law last year. Now, the two leaders' places in history are entwined again, as the Supreme Court prepares to hear two gay-marriage cases later this month.

After years of equivocation, Mr. Obama in recent months has planted himself firmly in favor of gay marriage, and his administration is now asking the court to strike down separate federal and state laws withholding marriage rights from same-sex couples. "American attitudes have evolved, just like mine have, pretty substantially and fairly quickly, and I think that's a good thing," Mr. Obama recently told ABC News. In 2012, for the first time, a slight majority of Americans favored same-sex marriage, according to data from the nonpartisan Pew Research Center, with young people especially supportive.

Read the complete story(Some news sites require registration)