HOUSTON – Julian Castro went on offense Thursday night and accused Vice President Joe Biden of being forgetful and not living up to the health care aspirations of President Barack Obama.

“I’m fulfilling the legacy of Barack Obama, and you’re not,” Castro said, after accusing Biden’s health care plan of leaving 10 million people uncovered.

“That’ll be a surprise to him,” a stunned Biden responded.

Castro, Obama’s former Housing and Urban Development secretary, tried to create a wedge between the former president and his vice president.

“We owe a debt of gratitude to President Barack Obama. Of course, I also worked for President Obama,” Castro said.

Then Castro turned to Biden: “I know that the problem with your plans is that it leaves 10 million people uncovered….Barack Obama’s vision was not to leave 10 million people uncovered.”

Biden pushed back and said Americans wouldn’t have to “buy” into his health care plan — which would expand upon Obamacare with a new government-run public insurance option.

“Are you forgetting what you just said two minutes ago?” Castro said to audible gasps in the audience.

“This is why presidential debates are becoming unwatchable,” Pete Buttigieg said after Castro and Biden argued over health care.

“That’s called an election,” Castro clapped back at the South Bend, Ind., mayor.

Sen. Amy Klobuchar then tried to tone down the debate: “A house divided cannot stand,” said the Minnesota senator, who also took on Bernie Sanders on his Medicare for All bill.