One of the most explosive moments of the Democratic debate in Houston was the face-off between former cabinet secretary Julian Castro and former Vice President Joe Biden over health care.

Castro accused Biden of changing his position in short order about the contours of his health care plan. "Are you forgetting what you said two minutes ago?" Castro asked Biden — a line that drew criticism from some commentators for suggesting that Biden, at 76, is having memory problems.

A look at the exchange and at Biden’s health care plan suggest that Castro is exaggerating any differences between Biden’s plan and his own, and is misleadingly interpreting what Biden said during the debate.

Let’s first look at Castro’s attack and Biden’s parries of his criticism:

CASTRO: "The problem with your plan is that it leaves 10 million people uncovered. … 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. They would automatically be enrolled. That’s a big difference. Because Barack Obama’s vision was not to leave 10 million uncovered. He wanted every single person in this country covered. My plan would do that. Your plan would not."

BIDEN: "They do not have to buy in. They do not have to buy in."

CASTRO: "You just said that! You just said that two minutes ago!"

BIDEN: "No."

CASTRO: "You just said two minutes ago that they would have to buy in!"

BIDEN: "I said if they cannot afford it!"

CASTRO: "You said they would have to buy in!"

BIDEN: "They would not have to buy in. If you qualified for Medicaid, they would automatically be enrolled."

CASTRO: "Are you forgetting what you said two minutes ago? Are you forgetting already what you said two minutes ago? I mean, I can’t believe you said two minutes ago that they had to buy in and now you’re saying you don’t have to buy in. You’re forgetting that!"

BIDEN: "I said anyone like your grandmother who has no money, you’re automatically enrolled."

CASTRO: "It automatically enrolls people regardless of whether they choose to opt in or not. If you lose your job, for instance, his health care plan would not automatically enroll you. You would have to opt in. My health care plan would. That's a big difference. I'm fulfilling the legacy of Barack Obama, and you're not."

BIDEN: "That'll be a surprise to him."

Castro’s criticism falls into two categories. We’ll look at them both.

Does Biden’s plan require people who want the public option to "opt in"?

Biden does require those who want Medicare coverage to "opt in," but this requirement is not nearly as significant as Castro makes it seem.

As described on his campaign website, Biden’s health care plan advocates "giving Americans a new choice, a public health insurance option like Medicare. If your insurance company isn’t doing right by you, you should have another, better choice. Whether you’re covered through your employer, buying your insurance on your own, or going without coverage altogether, the Biden Plan will give you the choice to purchase a public health insurance option like Medicare."

Biden’s plan would "ensure people making below 138% of the federal poverty level get covered. He’ll do this by automatically enrolling these individuals when they interact with certain institutions, such as public schools, or other programs for low-income populations, such as SNAP," or food stamps.

This tracks with what Biden said at one point in the debate — that "anyone who can't afford it gets automatically enrolled in the Medicare-type option we have."

On the surface, this is a difference with Castro’s plan. Castro’s proposal would "strengthen Medicare for those who have it, and expand it to achieve universal healthcare coverage by including all Americans within the program." Castro would "allow individuals to obtain supplementary private insurance or opt out of Medicare if they have a high-standard private insurance plan through an employer or organization that is regulated under the Affordable Care Act."

But Castro’s opt-out plan and Biden’s opt-in plan don’t seem significantly different.

Castro makes it sound like Biden’s opting-in process would be a noteworthy barrier. More likely, it would amount to a formality. Anyone who wanted the public option would have to request it and, presumably, sign forms like every other person seeking health insurance. But the important part is that they could not be rejected after they fill out those forms.

The distinction between filling out the paperwork to become part of the public option (as Biden would have it) and automatically becoming enrolled unless you actively reject it (which would, at some point, also require different paperwork) does not strike us as the "big difference" Castro touted.

Did Biden contradict himself?

Castro’s second line of attack was that Biden initially said people would have to opt in to Medicare and then later changed his tune and said they wouldn’t have to opt in.

Biden did say at several points before Castro challenged him that enrollment would be automatic — essentially a formality.

Biden said that "anyone who can't afford it gets automatically enrolled in the Medicare-type option we have."

He also said, "If you want Medicare, if you lose the job from your insurance — from your employer — you automatically can buy into this. No pre-existing condition can stop you from buying in. You get covered, period."

And Biden also said, "Every single person who is diagnosed with cancer or any other disease can automatically become part of this plan. They will not go bankrupt because of that. They will not go bankrupt because of that. They can join immediately."

These are consistent with Biden’s response to Castro’s attack, that Americans who need the Medicare option would "automatically be enrolled."

Our ruling

Castro said, "The difference between what I support and what you support, Vice President Biden, is that you require them to opt in (to a Medicare public option), and I would not require them to opt in. … They would automatically be enrolled. That’s a big difference." He also suggested Biden was contradicting what he’d said moments before.

Castro’s plan is an opt-out plan while Biden’s is an opt-in plan, but the differences between those are much less than Castro suggests. Biden’s plan would guarantee Americans who are in need access to Medicare coverage, just like Castro’s would. The differences would likely amount to the nature or timing of paperwork, rather than being significant barriers to access.

Castro used this questionable distinction to charge that Biden had said opposing things within two minutes, but that’s an exaggeration at best.

The statement has an element of truth but ignores critical facts that would give a different impression, so we rate it Mostly False.