In an interview with Barbara Walters airing Wednesday night, President Obama and first lady Michelle Obama discussed the photo of them that was attached to the most popular message in Twitter history: "Four more years." 

The picture tweeted out on election night as Obama won reelection -- which was chosen by the campaign's social media director -- was retweeted more than 810,000 times.  

The photo depicted the couple at a rally in Iowa, Obama explained. Why the hug? "Because I love my wife," Obama told Walters.

"I hadn't seen him in a while," the first lady added, because of the rigorous campaign schedule. "I walked onstage to greet him, and that's my honey giving me hugs."  

The president adds, "I love giving you hugs." 

If that exchange doesn't make you too uncomfortable, the whole interview airs on "Nightline" tonight.