It’s farmers market day on Union Square in New York, and Mimi Keo, a volunteer with "Organizing for Obama," is out canvassing for the president's effort to reform the health care system.

After his election last November, Barack Obama did not dissolve his impressive campaign organization. Thousands of volunteers are still enrolled, and stand by, ready to mobilize at the click of a mouse. And the president needs them now, for his intense fight to reform the health care system. "This is the first time I have done that. I just became a big Obama supporter early on and right now he needs me," says Keo.

The US Congress will vote on the reform package. So the idea is to convince senators and representatives that Obama has public opinion behind him.

The battle is also being waged on television, with ads from many organizations. In one ad, a Canadian patient explains that she had to come to the United States to get brain surgery because of the waiting lists that characterize the government-controlled Canadian system, says the ad. In fact, most studies show no more wait in Canada than in the US. But 15 years ago Bill Clinton’s reform failed because of fears of government-controlled medicine.

But this time, things might be different. Doctors, for example, are less opposed to the idea of health care reform than they were 15 years ago. For Robert Scher, an ophthalmologist in suburban New York, the current system is much too costly: "I have two employees in the back room that have to deal with the insurance company, which is money flowing out of the system. And that’s true of almost any physician in the United States: he or she deals with that bureaucracy all the time - that’s an insurance bureaucracy. And that has to be controlled because it costs money."

Since 1994, private insurance costs have more than doubled in the US. It’s a powerful argument for Barack Obama; but the battle is far from over. Health care industry lobbies, who spend tens of millions of dollars in Washington, are still a powerful voice and may have the last word.