Martin O'Malley, former governor of Maryland, participates in the first Democratic presidential debate last month in Las Vegas. (Photo by Josh Haner/Bloomberg)

Democratic presidential hopeful Martin O’Malley, who’s been struggling for attention, got some on social media Thursday. Ironically enough, it was the result of a Wall Street Journal photo caption that referred to him as “an unidentified man.”

The photo accompanied an online piece by columnist James Taranto about Sen. Bernie Sanders (I-Vt.) stepping up his criticism of Democratic front-runner Hillary Rodham Clinton. It showed Clinton, Sanders and O’Malley chatting at a recent event in Iowa attended by all three.

“Hillary Clinton, Bernie Sanders and an unidentified man backstage at the Iowa Jefferson-Jackson Dinner,” reads the caption.

“Oh dear. This is a brutal photo caption,” Matthew Gertz, the research director at Media Matters, a left-leaning watchdog group, said on Twitter. As of early Thursday night, his tweet had been retweeted nearly 1,000 times.

Throughout Thursday afternoon, there was a good deal of discussion about whether a caption writer didn't know who the former Maryland governor is or whether The Journal was making a mean joke about O’Malley.

In a statement Thursday evening, Paul Gigot, The Journal’s editorial page editor, made clear it was the latter.

"The caption is a joke about Martin O'Malley's obscurity as a Democratic presidential candidate,” Gigot said. “The photo ran with a column by James Taranto, who sometimes refers to ‘Martin O'Malley, whoever he is.’ Liberals need a better sense of humor."

O’Malley deputy campaign manager Lis Smith responded on Twitter, noting that the piece in question was more than a week old.

“Media Matters staffer takes week old caption out of context. Unlike you, we got the joke,” she wrote, adding a hastag: “#MediaFails”

Other O’Malley boosters -- and some independent observers -- noted that Media Matters was founded by David Brock, a Clinton supporter who is spearheading a super PAC working for her election as president.

The photo that appeared on Taranto’s column was taken by an Associated Press photographer. Among the Twitter traffic Thursday was a tweet that noted O’Malley had been identified by name when the AP first distributed the photo.