It was the kiss that stole the US president's limelight.

Barack Obama surprised the kids of the Daughter of Zion Jr Academy in Delray Beach, Florida with a drop-in photo op after a campaign event at Delray Beach Tennis Centre on Tuesday, Yahoo News reported.

The kids appeared excited, as one might imagine.

All except for a boy in the back row, who seemed a little preoccupied by the girl sitting next to him. So much so that he planted a kiss on her cheek while the camera clicked.

Obama's campaign later released the photo in a tweet captioned "Photo of the day." As of early Wednesday, it had been retweeted nearly 2000 times and "favourited" by over 1000 people.

Australia's Fairfax media pointed out that it was not the only time a candidate had been "photobombed" on the campaign trail, referring to an excited Denver man who posed with Mitt Romney at the Chipotle restaurant in Denver.

Marty Arps' alarming expression made headlines around the world, with him later explaining that: "I [did that] when I met Nicki Minaj. It's like, 'Ah, it's them, right there in front of you!' They're not from another world'."