Senator John D. Rockefeller hardly looks like the person who would fill part of the void left by the death of Senator Ted Kennedy. At 6-foot-6, thin as a pinstripe, and absent the gene that races for a camera, Rockefeller has, nonetheless, become the member of Congress as passionate about health-care reform as the Massachusetts senator was. In 1993, Rockefeller was an ardent but behind-the-scenes supporter of the Clintons’ sweeping health-care reform package, hosting the first closed-door strategy session at his Rock Creek Park estate, although Kennedy took the Senate lead.

This time around, Rockefeller is out front, operating under the klieg lights, so emotional at Senate Finance Committee hearings on the issue that he chokes back tears as he pleads with colleagues to rise to the occasion. The core of that plea is the public option, a national insurance plan akin to Medicare that would compete with the limited number of private companies providing insurance. It has pitted Rockefeller not just against Republicans, who don’t want reform of any sort even if it’s free, but also against other Democrats, including committee Chairman Max Baucus, who’ve gotten cover from the president’s less-than-absolute support of a public plan.

“Opposition to a public option is really just a vote for the insurance companies to make bigger profits, and that is unacceptable to me,” he says.

Now, barraged every day by millions of dollars' worth of lobbyists, the pragmatists in Congress have been persuaded that there are many other ways to get adequate reform—by accepting the industry’s voluntary concessions on things such as pre-existing conditions, through buyers’ co-ops (although the Congressional Budget Office says they would have little impact), regional companies, or a state option.

This is hokum, of course, and since returning from summer recess, Rockefeller has become the skunk at the garden party as he points out how all these counterproposals are a way of dodging what has to be done. A bill that doesn’t provide competition in the oligarchic private market would just be handing 47 million new customers to an untrustworthy industry (no wonder the industry is so gung ho!). “Opposition to a public option is really just a vote for the insurance companies to make bigger profits, and that is unacceptable to me,” he says.

Rockefeller knows there is more than one way to deny claims and myriad tactics to cherry pick customers—for example, by excluding from your network a sufficient number of doctors specializing in costly and complicated medical conditions. Moreover, there is no efficient way to enforce the new rules. Triggers have never worked, Rockefeller claims, and by the time one kicked in here, catastrophe for too many people would already have occurred.

• Benjamin Sarlin: The Ugliest Health-Care Debate• Watch: Wanda Sykes on Health CareThe Senate Finance Committee avoided even debating a public option until Rockefeller forced a vote on his amendment. As an indication of how fearful Democrats have become on reform, they split on the measure, defeating it. In explaining his no vote, Baucus, who theoretically favors the public option, said it was because he knew a bill with a public program would eventually lose. Apparently he decided to hasten the inevitable.

Like Kennedy, Rockefeller is unafraid to be liberal. Massive wealth (both top out on the forms disclosing personal wealth at “more than $500 million”) and a virtual lock on his Senate seat frees a man to do what he believes in. Coming from a family that believes in public service, Rockefeller, blessed or cursed to be as earnest as Al Gore, was raised in New York but signed on 45 years ago as a Vista volunteer in West Virginia, one of the country’s poorest states. When he described the privations of those coal miners and their children—like the boy Samuel stricken with leukemia who has exhausted his coverage—at a late night session last week, he teared up.

The current debate has brought Rockefeller out of the relative shell he’s occupied these past 24 years in Washington. Despite being a Rockefeller and marrying a senator’s daughter—a wedding that made the cover of Life magazine in 1967—the former West Virginia governor keeps a decidedly low profile. A student of Chinese and Japanese history, Rockefeller has his nose stuck in a book too often to go on TV, and, unlike Kennedy, doesn’t travel the social circuit. He leaves entertaining at their mansion, mostly for charitable causes, to his wife, Sharon Percy Rockefeller, the longtime CEO of Washington, D.C.’s flagship public TV station, WETA.

When the president called last week to appeal for Rockefeller’s vote for whatever bill emerges from the committee, the senator said he was “noncommittal.” Barring some last-minute miracle, that bill, expected later this week, won’t contain a public option. “With so much at stake, I always come back to my experiences more than 45 years ago in the small coal mining town of Emmons, West Virginia,” Rockefeller says. “I witnessed the tragic failings of our broken system firsthand, and since those days I have seen the situation grow worse—not better. The injustice and unimaginable challenges for countless hard-working Americans just has to stop. Period.”

There will be other opportunities to revive the public option—when the Finance Committee bill gets merged with another Senate bill, during the floor fight to get the merged bill passed, and then in conference to reconcile whatever comes out of the Senate with what’s already passed in the House, which contains a public option. Kennedy believed in miracles. Rockfeller does, too.

Margaret Carlson is a columnist for Bloomberg News. She was a columnist and deputy Washington bureau chief for Time magazine.