With a final Senate health care bill still under negotiation, Sen. Jay Rockefeller (D-W.Va.) on Friday went on the attack against one proposal being given serious consideration by the Democratic leadership and President Barack Obama: a “trigger— for the public insurance option.

In a statement, Rockefeller criticized the idea of a plan that would only allow for the public insurance option if private insurers failed to adequately lower prices. However, Rockefeller voted for a reform bill in the Finance Committee even though that legislation did not include a public insurance option.

The White House and Senate Majority Leader Harry Reid (D-Nev.) are intrigued by the trigger because it is favored by moderate GOP Sen. Olympia Snowe (Maine). Obama would like Snowe’s vote to give any final bill an air of bipartisanship; Reid also wants her vote and believes it would attract the support of skeptical Democratic moderates.

But Rockefeller, a leading liberal voice in the health care debate, said the trigger is a bad idea that will fail to lower insurance costs. “Historically, trigger mechanisms have not been successful, and they are not a substitute for a strong public health insurance option,— Rockefeller said. “A trigger simply delays price competition, which in turn will delay affordability for consumers and moves us farther away from the goals of health care reform. Already, we are seeing insurance companies threatening to game the system, by raising their prices in advance of reform. The only way to curb price-gouging by health insurance companies is with real competition on Day One — that is the public option.—