On the narrow substance of the issue, she’s right. Focusing only on taxes is pointless. But in a larger way, she’s wrong.

The No. 1 reason to question her version of Medicare for All — in which private health insurance would be eliminated — is its political viability. It would be an enormous disruption to the health care system, and history shows that health care disruptions are very hard to pass and usually unpopular at first. Polls show that her plan is already unpopular, and it would be a bigger disruption than Obamacare or Bill Clinton’s failed plan.

Given all that, she needs to engage with the political realities — with how she would overcome people’s resistance to giving up their health insurance for a larger new program that, yes, would require a tax increase.

I think Warren has run an excellent campaign on the whole, and I think she has the most thoughtful agenda for addressing the stagnating living standards of most Americans. I’m surprised that she has chosen to focus so much of her candidacy on the most aggressive version of Medicare for All. But she has. Now it’s time for her to tell voters how she will deal with the politics of passing it.

In my view, her best answer involves finding a way to signal her openness to a transition, in which people who want to keep their private insurance can do so (and taxes don’t yet need to rise) while Medicare initially expands voluntarily. That idea is hugely popular.