A photo caption published Thursday afternoon by The Wall Street Journal set reporters aflutter, as many noticed that Democratic presidential candidate and former Maryland Gov. Martin O'Malley was listed only as an "unidentified man."

The picture, which was featured in a Journal op-ed penned by conservative columnist James Taranto, comes from the Associated Press. The caption, however, comes from Taranto.

"The caption is a joke about Martin O'Malley's obscurity as a Democratic presidential candidate," a Wall Street Journal spokesman told CNNMoney's Dylan Byers.

The Democratic presidential primary has until this week seen the party's candidates — former Secretary of State Hillary Clinton, Sen. Bernie Sanders, I-Vt., and O'Malley — giving each other the kid glove treatment, the op-ed read.

But that appears to be changing.

"Maybe that Democratic debate wasn't as much of a love-in as everyone (except this columnist) thought it was," read his op-ed, titled, "Slow Bern Sanders finally starts criticizing Mrs. Clinton."

"Hillary Clinton and Bernie Sanders, the two remaining candidates for the nomination apart from that other guy, are finally feuding unambiguously," he added.

When the story went online Thursday afternoon, newsrooms everywhere took note of the photo's caption. "Oh dear. This is a brutal photo caption," said Media Matter's Matthew Gertz.

Byers said originally, "this has to be fake, no?"

MSNBC's Alex Seitz-Wald added, "That can't be real ... ?"

However, as Taranto's penchant for dry and mischievous humor is well known in media circles, many guessed quickly that the photo caption was a gag from the author, and not the Journal's editors.

"It's kinda sad that we all thought it was possible the WSJ actually didn't recognize O'Malley, though," the Huffington Post's Elise Foley said.

Clinton is easily the Democratic front-runner, and she leads by 54.8 percent to Sander's 32.5 and O'Malley's 1.8, according to RealClearPolitics' polling average.