Independent Sen. Bernie Sanders of Vermont has no idea how much the revolution will cost.

You will have to elect him to find out.

The senator declared this weekend during an interview with CBS News that it is “impossible” to know the price of his agenda. It was a shocking and possibly disqualifying moment. It was also a moment that you will not see imitated during the general election should Sanders become the Democratic nominee.

CBS's Norah O’Donnell began by asking: “Your agenda has promised free healthcare for everybody, free college tuition, and to pay off people’s college loans. The price tag for that is estimated to be $60 trillion over 10 years, correct?”

“Well look, we have political opponents who come up – ” Sanders started to say.

“You don’t know how much your plan costs?” the anchor interjected.

Sanders said, “You don’t know, nobody knows, this is impossible.”

That $60 trillion price tag, by the way, comes from a CNN analysis that does not even include all of Sanders’s proposed agenda items. In other words, $60 trillion is a conservative estimate.

“You’re going to propose a plan to the American people, and you’re not going to tell them how much it costs?” O’Donnell continued.

“Of course I will,” the senator said. “You know exactly what healthcare costs will be, one minute, in the next 10 years if we do nothing. It will be a lot more expensive than a 'Medicare for all' single-payer system.”

It was a good moment for O’Donnell. She was firm and insistent. She asked legitimate questions, which raised bigger questions about the seriousness of the Sanders campaign. It was a good moment for journalism, one where a member of the free press held a member of the ruling party to account.

It was also a moment you 100% will not see repeated in the general election should Sanders win the Democratic nomination. He is polling in second place behind former Vice President Joe Biden. There is a chance the Vermont senator could win this thing. If Sanders goes into the 2020 general election against President Trump and the Republican Party, there is no version of reality where the Norah O’Donnells of the world pepper the senator with legitimate and possibly damaging questions about the feasibility of his platform.

Enjoy these spontaneous acts of journalism while they last. They come and go depending on the needs of the Democratic Party.