For all this furor (see also this post), I do think liberal groups and unions are saber-rattling. Given the option of getting something they’re not happy with or getting nothing at all, they’ll take the former, a foot in the door. See the last paragraph of the following article, from the Huffington Post, today:

The nation’s largest union group said Thursday that it will not support the Democratic health-care bill unless “substantial changes” are made to the current Senate version.
AFL-CIO President Richard Trumka said in a statement to reporters that without a public option for insurance coverage or an employer mandate – and with a tax on high-end insurance plans that some union members get – the health care legislation supported by Senate Democrats falls far short of meeting his group’s standards….

The remarks are a strong indication that the coalition of pro-health-care-reform groups has begun to fray.
Earlier in the day, Service Employees International Union President Andy Stern penned a letter to his fellow union members in which he called out President Barack Obama for abandoning his own principles of reform….

Stern, like Trumka, called for Democrats to make changes to the legislation as the process moves forward. And his rebuke of Obama – a staunch personal ally – was a telling sign of the growing frustration within the labor movement.
Both labor leaders were particularly incensed over the concessions made by the Senate’s Democratic leadership to Sen. Joseph Lieberman (I-CT), the 60th member of their caucus. “The public option is declared impossible. Americans cannot purchase Medicare at an earlier age. The health insurance reform effort we have needed for a century is at risk,” Stern wrote.
Officials at both unions met late into the night on Wednesday in emergency sessions to discuss the Senate bill. Aides say the conversations were lengthy and, at times, emotional. The labor community, while privately angry with the White House and Democrats in Congress, still needs the support of these lawmakers on other legislative priorities. Meanwhile, having poured millions into advertisement and man-hours in order to get health care passed, they have watched in horror as the principles they worked for were abandoned in a matter of days.
Officials are also aware of how much would be lost by simply scrapping the bill altogether. Stern noted that under the Senate’s bill 30 million additional people would be covered, pre-existing conditions would no longer be an excuse to deny coverage, and people who get sick would no longer lose their insurance….