Former Maryland Gov. Martin O’Malley says it’s easy to see why Bernie Sanders is tapping into the populist anger: He’s a socialist.

In an interview Friday with TIME at a coffee shop in Portsmouth, N.H., the Democratic long-shot contender reflected on his inability yet to break out in the race for the White House in a year in which voters in both parties are frustrated with Washington, as well as Bernie Sanders’ ability to emerge as a challenger to Clinton.

“Yeah, he sure was,” O’Malley said, commending Sanders on his success, before laying down his explanation. “I don’t take anything away from him by being the socialist challenger to the Democratic Party.”

O’Malley has campaigned relentlessly over the past year with only incremental results in the three-person Democratic field. He averages just 2% in national Democratic polls, while notching about 5% in Iowa and 3% in New Hampshire. He said Sanders, who is leading Hillary Clinton in New Hampshire and closing the gap in Iowa, had advantages that he did not.

“It really screamed not establishment in ways I couldn’t,” O’Malley continued, about Sanders’ political philosophy. “I’m a lifelong Democrat. I’m proud of it. But I could not out-anti-establishment the first socialist to join the Democratic Party to run for president. That’s pretty anti-establishment.”

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