Houston – Democratic presidential hopefuls clashed over competing health care plans, foreign policy and education plans. But the divide that shaped the third debate was a fight over which candidate lived up to President Barack Obama's ideals.

Throughout the three-hour event Thursday at Texas Southern University, former Vice President Joe Biden wrapped himself in Obama’s legacy, presenting himself as both a partner in his legislative achievements and the heir to his political agenda.

Sharing the stage with his top rivals for the first time, Biden faced sharpening attacks from liberal adversaries who accused him of a modest political approach at a time when ambitious overhauls are needed to counter President Donald Trump.

More: At Democratic debate, Biden at center stage and center of attacks

Biden set the toneearly during a clash on health care with U.S. Sen. Elizabeth Warren, when he said her support for “Medicare for all” that would eliminate private insurance veered toward U.S. Sen. Bernie Sanders’ wing of the party.

“The senator says she’s for Bernie,” he said of Warren. “Well, I’m for Barack – I think Obamacare worked.”

Though Obama remains a popular and iconic figure among many Democrats, Biden’s snug embrace of his legacy continued to pose a challenge for him. When confronted with fresh criticism of the Obama administration’s policies, Biden was apt to deflect.

That’s what happened when Jorge Ramos, one of the ABC-sponsored debate’s moderators, questioned whether Biden had done enough to oppose deporting people in the country illegally. Biden dodged, saying his role was as “the vice president of the United States.”

Julian Castro, the former U.S. housing secretary and a Texan playing to a home-state crowd, interrupted with a bruising response.

“Every time something good about Barack Obama comes up, he says, ‘Oh, I was there, I was there, I was there,’” said Castro. “And then every time somebody questions part of the administration that we were both part of, he says, ‘Well, that was the president.’”

Biden curtly responded that he stands by Obama’s record – “good, bad and indifferent.”

Castro, who was the most willing to confront Biden, had an even more striking exchange when he questioned whether the 76-year-old is “forgetting already” an element of his health care plan that he misstated.

Then came Castro's stinging insult: "I'm fulfilling the legacy of Barack Obama," he said, "and you're not."

“That would be a surprise to him,” Biden shot back.