Little by little, Congressional Dems are beginning to pin the lion’s share of the blame for the badly weakened health care bill on a single figure: President Obama.

Here’s Russ Feingold, for instance, making a striking accusation: Obama may be more to blame than Joe Lieberman for the current state of play…

“This bill appears to be legislation that the president wanted in the first place, so I don’t think focusing it on Lieberman really hits the truth,” said Feingold.

While Feingold and others have repeatedly called on Obama to use the bully pulpit more aggressively on health care, they’ve refrained from implying that Obama wants a bill without the key liberal provisions he claimed to be seeking, as Feingold does here.

Meanwhile, here’s Anthony Weiner, making the surprisingly aggressive accusation that Obama’s lackluster leadership is to blame for letting the process get hijacked by Lieberman et al:

“Snowe? Stupak? Lieberman? Who left these people in charge? It’s time for the President to get his hands dirty. Some of us have compromised our compromised compromise. We need the President to stand up for the values our party shares. We must stop letting the tail wag the dog of this debate.”

This case, to be sure, is one that we’ve been hearing on the left — from bloggers and activists — for months. But it wasn’t one you heard from Congressional Dems who have to work regularly with the President.

Now that’s changing — and it’s a dynamic to watch. It’s another measure of the extreme frustration among liberals and Dems over the failure (so far) to leverage the Dem majority behind an agenda that reflects core liberal priorities and aspirations.