CONGRESSIONAL LIBERALS SPEAK UP…. When it comes to health care reform, most of the recent debate has been focused on how to weaken the bill and make conservatives happy. In the Senate, that’s led a band of six centrists and center-right members to hold up the process and strip reform of measures Democrats find important. In the House, it’s a matter of satisfying the demands of center-right Blue Dogs.

The group that’s left out of the equation, and whose concerns seem less pertinent right now, is the majority of the majority — namely, liberal/progressive Democrats.

Roll Call reports this afternoon that a group of progressive House Dems “voiced their concerns” to Speaker Pelosi today, fearful that Blue Dogs and Senate Finance Chairman Max Baucus (D-Mont.) are, deliberately or not, sabotaging this once-in-a-generation effort.

About two dozen liberal Members trickled in and out of the hour-long meeting with Pelosi, who discussed strategy for moving the bill forward if Energy and Commerce Chairman Henry Waxman (D-Calif.) is unable to reach a deal with Blue Dogs this week.

“There was a lot of talk about the Blue Dogs,” said one lawmaker, who noted that Pelosi is walking “a very delicate line” as she tries to keep a Democratic coalition together on the bill.

“She won’t criticize them. She says they’re representing their constituents. She’s being very careful. But other Members are not being as charitable,” said the progressive Democrat.

Here’s the problem — or the nightmare, depending on one’s perspective — that often goes unstated: liberal lawmakers feel as if they don’t have any leverage right now. And they’re right.

Progressive members of Congress are already on board with reform. They like the tri-committee proposal in the House, and fully embrace the HELP committee’s bill in the Senate. They don’t need coaxing or deals or enticements or concessions. They have legislation they like, and there’s not much more for them to talk about.

For conservatives, it’s obviously an entirely different dynamic. Conservatives don’t really want to overhaul the system. Democrats on the right are skeptical of the approach, and Republicans on the right oppose reform in a more fundamental way. If reform has to be “bipartisan,” and can’t pass the House without Blue Dogs, that necessarily means making the bill worse.

It also means conservatives have the leverage. If they don’t get the changes they want, they’ll kill reform and do extraordinary damage to the Obama presidency — an outcome they don’t consider especially troublesome. If conservatives do get the changes they want, it’s assumed liberals will go along, because some reform will be preferable to the status quo, and they have a vested interest in not undermining the White House.

So, it becomes easier to imagine a scenario in the fall in which center-right lawmakers — some Democrats, some not; some in the Senate, some not — hold reform hostage until it looks like the kind of bill they want. The left is told, “Take it or leave it.” If liberals say it’s a bridge too far, conservatives will say, “We had a bipartisan bill ready to go, but the left killed health care.” If liberals swallow hard and accept it, the once-in-a-generation opportunity will have passed, and a weak bill will become law.

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Steve Benen

Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.