Going into Thursday’s debate, most pundits predicted it’d be a gang-up on former Vice President Joe Biden, the current front-runner. Instead, nearly all of the direct attacks were handled by Julián Castro.

Castro, who served as Housing and Urban Development Secretary during President Barack Obama’s administration, went after Biden multiple times during the debate and accused the former vice president of not fulfilling Obama’s legacy.

Early on in the debate, the two sparred over their differing health care plans, with Castro backing a “Medicare-for-all” proposal and Biden supporting a more-moderate approach that would build on the Affordable Care Act. But it was Castro who went on the attack by claiming that not only would Biden’s plan leave out millions of people, the vice president didn’t even appear to remember his own policy.

“The difference between what I support and what you support, Vice President Biden, is that you require them to opt in, and I would not require them to opt in” Castro said. “They would automatically be enrolled.”

“They do not have to buy in,” Biden shot back, defending his plan.

“You just said two minutes ago they would have to buy in,” Castro shot back. “Are you forgetting what you said just two minutes ago?”

While the moment quickly went viral on social media, the Daily Beast’s Lachlan Markay pointed out that Castro was incorrect — Biden didn’t actually say people would have to opt in to his plan. Instead, he said the exact opposite just a minute before the widely shared exchange.

“Anyone who can’t afford it gets automatically enrolled in the Medicare-type option we have,” Biden said of his plan.

Markay wasn’t the only political pundit to point out that Castro was wrong. The Washington Post’s Amber Phillips analyzed the exchange, and concluded that on the substance of the question, Castro was wrong.

“A risky move for Castro just became riskier: He called out Biden in a way that could be considered below-the-belt. And he didn’t nail the substance,” Phillips noted.

“Castro is throwing long with great risk,” former Obama senior advisor David Axelrod wrote on Twitter after the exchange.

Despite the risk, Castro pounced on Biden later in the debate, claiming the former vice president attempted to “take credit” for the well-liked parts of Obama’s legacy while avoiding discussion about criticism of his administration.

“He wants to take credit for Obama’s work but not have to answer to any questions,” Castro said.

“I stand with Obama — good, bad, and indifferent,” Biden responded.