Liberal groups that have bankrolled much of the media campaign defending the Democrats’ health reform efforts reacted angrily Wednesday to reports that Senate Democrats may ditch, or significantly shrink, a public insurance option to win over moderates.“We don’t think it is a compromise. It is a cave-in,— said Ilyse Hogue, a spokeswoman for MoveOn.org, which has spent millions of dollars this year promoting legislation and attacking critics.MoveOn.org and other progressive groups were dismayed by a tentative deal reached by moderate and liberal Senators on Tuesday evening that would offer alternatives to the public option. Under the proposal, the Office of Personnel Management would negotiate with private insurance companies to offer health plans to individuals much as it does for federal employees and lawmakers.People between the ages of 55 and 64 would be allowed to enroll in Medicare, the government-run health insurance plan now available only to seniors 65 and older. The plan would provide for future creation of a public plan if the private companies could not provide adequate coverage.But an official with Health Care for America Now, a coalition of union and liberal groups, said the Medicare buy-in and government-administered private program were not sufficient substitutes for the public option available to all age groups.“We’re glad there is a public option for people 55 and older and deeply disappointed that there doesn’t seem to be a public option for people under 55,— said Jacki Schechner, a spokeswoman for HCAN, which has underwritten a multimillion-dollar ad campaign supporting the health care overhaul.Schechner said her group would continue to press Senators to support a full public option.Even before the Senate deal was unveiled, HCAN announced a new round of cable television spots, which urge viewers to “tell Congress we need good health care we can afford with the choice of a public insurance option now.—The $350,000 ad buy will run for a week on CNN and MSNBC.Hoping to rally liberal supporters, MoveOn also sent out an e-mail to its members Wednesday alerting them to the potential deal reached in the Senate.“Instead of pulling out all the stops, they’ve bargained away the heart of health reform — allowing conservative senators like Joe Lieberman and Ben Nelson to hold the process hostage and protect Big Insurance,— the e-mail stated. The e-mail asks members to add their name to a petition to be sent to Congress and President Barack Obama, adding “don’t give in to conservatives and Big Insurance.—Sens. Lieberman (ID-Conn.) and Nelson (D-Neb.) have indicated they could not vote for a health care plan that included a public option.Another liberal group, the Progressive Change Campaign Committee PAC, also launched an online petition urging liberal Senators to block any compromise. The petition will be delivered to four Senators who have been staunch backers of the public option: Russ Feingold (D-Wis.), Bernie Sanders (I-Vt.), Roland Burris (D-Ill.) and Sherrod Brown (D-Ohio).While conservative groups have lambasted the public option, they did not appear to be won over by the compromise.Americans for Prosperity, a conservative group that helped spearhead town hall protests against the health care plan last August, issued a release titled, “Reid’s public option compromise places politics over patients.— The group along with other conservative organizations are planning a Tuesday rally at the Capitol.While estimates show the proposed public option would likely be used by a small fraction of Americans, it has drawn outsized attention from both opponents and proponents of health care reform.“It is highly emotional and sometimes radioactive,— said Jim Dau, a spokesman for the senior citizens advocacy group AARP.Dau said AARP has not been involved in the Senate negotiations over substitutes for the public health insurance plan.“We are happy to look at it when it is in writing,— he said.Dau said the seniors group wanted to see more fleshed-out details on various aspects such as the Medicare buy-in, which could affect the group’s membership.Dau said allowing people 55 or older to buy into Medicare could work well “if done the right way.— But he warned it could also “make Medicare a national de facto high-risk [insurance] pool.—