Sometime this morning, House Energy and Commerce Committee Chairman Henry Waxman will dash into a phone booth, and re-emerge. What happens next remains to be seen.

House efforts to pass a meaningful healthcare reform bill are now at an interesting juncture. Liberals have finally rebelled at the disproportionate clout Blue Dog Democrats seem to routinely exercise over the content of significant legislation. Waxman proposes to pour oil over troubled waters at a mass question-and-answer session for the entire Democratic Caucus this morning.

House Speaker Nancy Pelosi spent half of Wednesday finalizing a deal with the Blue Dogs — and the other half quelling a brewing rebellion among progressives who think conservatives have hijacked health care reform.

Liberals, Hispanics and African-American members — Pelosi’s most loyal base of support — are feeling betrayed after House Energy and Commerce Committee Chairman Henry Waxman (D-Calif.) reached an agreement with four of seven Blue Dogs on his committee who had been bottling up the bill over concerns about cost.

The compromise, which still must be reconciled with competing House and Senate versions, would significantly weaken the public option favored by liberals by delinking reimbursement rates to Medicare.

“Waxman made a deal that is unacceptable,” said Rep. Jerrold Nadler (D-N.Y.), one of about 10 progressives who met repeatedly with Pelosi and Majority Leader Steny Hoyer (D-Md.) on Wednesday.

“We signed a pledge to reject any plan that doesn’t include a robust public option, and this plan doesn’t have a robust public option,” he added.

By sundown Wednesday, the outcry from the left had become so loud that Waxman was forced to scrap a scheduled markup of the compromise measure. He rescheduled the meeting for Thursday morning and convened a mass question-and-answer session for a deeply divided Democratic Caucus — a meeting that is expected to be extremely contentious.

Two months ago, most of the 80-plus members of the Congressional Progressive Caucus signed a pledge that they would oppose any health care bill that didn’t contain a bona fide public option that would compete with private insurers.

On Wednesday, they seemed willing to stick to their promise.

CPC Chairwoman Lynn Woolsey (D-Calif.) emerged from her meeting with Pelosi to tell reporters that the Blue Dog deal needed to be “much stronger to get our support.”

House Financial Services Committee Chairman Barney Frank (D-Mass.) predicted that House liberals, who believe they have compromised away several core issues to further President Barack Obama’s agenda, might finally buck leadership if they are force-fed a weakened public option.

“I don’t think it would pass the House — I wouldn’t vote for it,” Frank, a CPC member, told POLITICO.

He answered “yes” emphatically when asked if progressives were willing to delay the entire process as the Blue Dogs have done.

Frank said liberals are becoming increasingly leery of the clout wielded by Blue Dogs …

The key issue for progressives is probably the delinking of reimbursement rates to Medicare. Progressives are committed to a robust, bona fide public option, one that will actually exert pressure on private insurers to cut their premiums. The biggest threat to real reform is a toothless public plan that seeks to create a level playing field by neutering the public plan’s potential cost advantage.

However, it’s not at all clear that delinking reimbursement rates to Medicare would, in fact, significantly weaken the public option. Even if reimbursement rates are not linked to Medicare, the public plan should still be able to negotiate rates that would exert significant downward price pressure in the insurance market.

Presumably, Waxman is confident that he can persuade progressives of this at the mass question-and-answer session this morning. However, clearly, the delinking of reimbursement rates to Medicare was sold to Blue Dog Democrats as a major concession. If Waxman can find language that actually manages to mollify progressives without getting Blue Dogs’ backs up, that will be a truly superhuman achievement, in my opinion.