In a dramatic vote of confidence, Howard Dean—who as recently as last week said a bill without the public option “should be defeated”—helped broker and strongly endorsed the current Senate health care compromise yesterday, calling the Medicare buy-in proposal a “big step forward.”

"There had to be a public option because the private sector doesn't work,” Dean told the Huffington Post. “And if they can make it work [without a public option], then let's see."

That’s probably as far as Dean has ever strayed on this issue from his netroots base, which is irate over the current state of affairs. "How could they?" MoveOn demands, exhorting their members to pressure fence-sitting senators to “unravel this deal.” Health Care for America Now and FireDogLake are similarly incensed. Even Democracy for America, Dean’s former campaign group, is holding the line. “The continued talk of finding a ‘compromise’ in the Senate which would eliminate the public option in the health care bill is a negotiation with defeat,” their latest mailing blares. (Click here to read Jonathan Cohn's ten questions about the public option compromise).

There are certainly folks who would welcome Dean to the pragmatist fold. And the public-option-or-bust crowd hasn’t really called Dean out for his concession to political reality. Jim Dean, who runs Democracy for America, explained that his brother is "just trying to move this ball forward one step at a time. He hasn't really passed judgment on the entire package because nobody knows what it is yet."

But it does seem that the left has lost one of its standard-bearers—Dean’s switch gives moderates cover to settle for something less than the robust public option they may have otherwise supported. Adam Green, with the Progressive Change Campaign Committee, says Dean’s decision “dilutes” the effort.

“It seems like there’s a disconnect between these pundit-like opinion leaders and the actual grassroots,” Green told me, saying he was surprised when he heard Dean—and other public option boosters, like Anthony Weiner—supported the compromise. “They’re approaching it very academically, as opposed to asking the question, what do you tell a 25 or 30-year-old who worked for your campaign, worked for President Obama, has now been working for months for health care reform, and is now being told, well, they don’t get real reform for another 30 years?”