Healthcare is clearly the primary topic in this week’s second round of Democratic primary debates, but Obamacare — the crowning jewel of former President Barack Obama’s liberal agenda — seems to be a taboo subject.

The only Democratic presidential candidate who seems to still support Obamacare is the man who helped push it through: former Vice President Joe Biden.

Most of the candidates have endorsed “Medicare for all” or rolled out their own healthcare plans, some of which include public buy-in options. In doing so, they’re implicitly admitting that Obamacare has failed to live up to its promises.

Even Biden, who has rejected a “Medicare for all” system in favor of building on the Affordable Care Act, introduced his own healthcare plan to expand subsidies in the existing program while creating a public option that would be available to those who want it.

By campaigning against “Medicare for all,” Biden hopes to win over the moderate voters who oppose the elimination of private insurance plans — and there’s a lot of them. He understands that the higher cost and lower quality of socialized healthcare is a threat to most middle-class families, and that most voters are content with the plans they have now. Passing “Medicare for all” would mean getting “rid of Obamacare,” he said.

But the underlying agreement in the healthcare debate is that Obamacare has failed. And by introducing his own plan, Biden has made this admission as well. Obamacare was supposed to guarantee access and lower costs over its decadelong roll out, but this is the same promise Biden, and the other Democratic candidates, are making now. It’s an expensive promise, one that would cost Americans more than $750 billion over the next decade, according to his campaign. All that, just to do what Obamacare was supposed to have already done.

Of course, Biden can’t admit that Obamacare failed to deliver: to do so would be to admit that he, and Obama, failed. The other candidates won’t say it either. Obamacare is still considered a sweeping success with the base, and to explicitly run against it would be libelous among a voter base that considers Obama a liberal hero.

Obamacare will continue to be the elephant in the room until the Democratic candidates vocally admit what their policies have said for them: it isn’t working. Sure, the specifics differ. Biden wants to build on the existing system while the other candidates attempt to overhaul it. But the truth is that if Obamacare was doing what it was supposed to do, this wouldn’t be a debate at all.