Presidential candidate Julian Castro accused former Vice President Joe Biden of forgetting and changing details about his proposed health care plan during the Democratic debate Thursday night.

Some people viewed the attack on 76-year-old Biden as ageist, but Castro has denied any correlation between the statement and Biden’s age. The moment occurred when the former Housing and Urban Development Secretary tried to differentiate between his proposed healthcare plan and Biden’s.

“The problem with your plan is that it leave 10 million people uncovered,” said Castro. “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.”

Biden responded by saying they would not have to buy him, prompting Castro’s heated response.

In the most-tweeted about moment of the night, Castro asked Biden, “Are you forgetting what you said two minutes ago?”

“Are you forgetting already what you said just two minutes ago?” he repeated.

Castro defended his comments Friday morning saying it “was not a personal attack.”

“This was about a disagreement over what the vice president said regarding health care policy,” Castro told CNN. “I pointed out this big difference in our approach and, no, Americans need to know that,” he said.

Earlier in the debate, Biden used the phrase “buying in” when outlining his healthcare plan to the other candidates.

The option I’m proposing is Medicare-for-all — Medicare for choice. If you want Medicare, if you lose the job from your insurance — from your employer, you automatically can buy in to this. You don’t have — no preexisting condition can stop you from buying in.”

However, Castro likely took this out of context, not mentioning that Biden also said that “anyone who can’t afford it gets automatically enrolled in the Medicare-type option we have.”

Biden has recently been under scrutiny for a series of misstatements, including saying that poor kids are just as bright as “white kids.”

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