Marco Rubio often pitches himself as the candidate of the future, but when it comes to the issue of same-sex marriage, he's something of a throwback.

The Republican presidential candidate said Sunday that he disagrees with the recent Supreme Court decision that legalized same-sex marriage nationwide and does not consider it to be settled law.

“It is the current law. I don't believe any case law is settled law. Any future Supreme Court can change it,” Rubio said on NBC’s Meet The Press, referring to the landmark June 2015 ruling. “And ultimately, I will appoint Supreme Court justices that will interpret the Constitution as originally constructed.”

On Monday, Rubio rolled out a new campaign ad in which he appeals to Americans who "feel out of place in our own country," including "millions with traditional values branded bigots and haters."

While every major Republican candidate opposes gay marriage, Rubio's position clashes with generational change in the U.S. A Pew Research Center poll in July found that it is supported by 70 percent of Millennials (born in 1981 or later) and 59 percent of Generation X (born 1965-1980), while just 45 percent of Baby Boomers and 39 percent of the Silent Generation wants it to be legal.

(Chart by Pew Research Center)

On Meet The Press, Rubio labeled the 5 to 4 decision "bad law," arguing that states should be allowed to restrict marriage to opposite-sex couples, defending it as a "traditional and age-old institution." Unlike Hillary Clinton, who came out for gay marriage in 2013, Rubio has consistently opposed it. (He also recently told the Christian Broadcasting Network he’d overturn President Barack Obama’s executive order aimed at prohibiting federal contractors from making employment decisions on the basis of a person's sexual orientation or gender identity.)

Rubio's Dilemma

Opposition to same-sex marriage gives Democrats ammunition against Rubio’s core message that he’s the candidate that best reflects the future of America. “If I am our nominee, they will be the party of the past, and we will be the party of the future,” Rubio said to cheers and applause during the Nov. 10 Republican debate. The generational message, which Obama successfully deployed against Hillary Clinton in 2008, is widely seen as a boon to Rubio in a hypothetical general election against Clinton, the favorite for the 2016 Democratic nomination.

A new NBC/Wall Street Journal national poll finds Clinton and Rubio tied 45-45 percent head-to-head among voters aged 18 to 34, traditionally a stronghold for Democrats.

The divide over same-sex marriage encapsulates Rubio’s dilemma: he’s a young face in a party dominated by older voters. The Pew poll found that while a majority of Americans want gay couples to be able to marry, just 32 percent of Republicans and 24 percent of white evangelical protestants support it. In a candid election postmortem in 2013, the Republican National Committee acknowledged the "generational difference" on gay rights and warned, "If our Party is not welcoming and inclusive, young people and increasingly other voters will continue to tune us out."

Senator Ted Cruz has proposed a constitutional amendment to reverse the Supreme Court ruling and let states outlaw it. Rubio is not supporting such an amendment, and argued on Sunday that it "would be conceding that the current Constitution is somehow wrong and needs to be fixed."

Younger Americans

In some ways, Rubio is more relatable to younger Americans. As he often reminds voters in debates and stump speeches, he didn't pay off his student loan debt until just a few years ago. The son of Cuban immigrants, Rubio represents America's diversifying youth. He’s also a follower of hip-hop music.

"I'm a big fan. He's got a nice story," said Grace Cunnie, an 18-year-old freshman at Saint Anselm College in New Hampshire who attended a Rubio campaign event there last month. "He has a very relatable story."

The generational message doesn’t translate as well on a policy level.

Surveys indicate that Clinton is more in tune with younger generations than Rubio on issues such as raising the federal minimum wage, normalizing relations with Cuba and loosening marijuana laws. While Clinton (like majorities of young voters) favors these ideas, Rubio opposes a wage hike, vows to reverse Obama’s move to open diplomatic relations with Cuba and said in August he'd enforce anti-marijuana federal laws in states that have legalized pot, like Colorado and Washington.

Regardless, some younger Republicans are drawn to Rubio's pitch.

"I really like how he talks about how the 21st century can be the best years for America," said Joshua Gagne, a 19-year-old college freshman in New Hampshire. "He's got a very positive message, unlike some of the other candidates."

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