Gingrich and Romney are facing questions about conduct earlier in their lives. But even the squeaky-clean Pennsylvanian is dogged by questions from his past.

If there's been one overarching theme to the Republican presidential primary in the last week or two, it's been that past coming back to haunt the contenders. For Newt Gingrich, there's the coming interview with his second ex-wife, Marianne, in which she accuses him of asking for an open marriage. For Mitt Romney, it's been his career in private equity, a credential that seemed custom-made for the business-friendly GOP but has instead proved a millstone around his neck.

What about Rick Santorum, you ask? Clearly, it's this embarrassing yearbook photo, which The Atlantic first unearthed in May 2011 and which has been making the rounds around the Internet on Thursday. On the trail in South Carolina on Wednesday, Santorum -- in a not-so-veiled swipe at Gingrich -- said that he's never so much as sat on a couch with a woman other than his wife. It's tempting to blame that on the sideburns and vaguely flowered shirt seen in this photo, but, hey, it was the '70s.

You can see scrapbook treasures from the whole GOP field, including a few candidates who have since dropped out, in the gallery below.

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