For the law to succeed, groups such as Enroll America, whose officials include several veterans of Obama campaigns, will need to cajole millions of Americans, including many healthy ones, to enter the insurance market. It could be a tough sell. Confusion about the law is rampant. The online insurance sites, which open for enrollment Oct. 1, could be tricky. Some people who rarely need medical care might view even low-cost health plans as too pricey.

And while advocates say that knocking on doors is one way to overcome these challenges, skeptics point out that such canvassing, which is modeled on successful political campaigns, is untested for a complex national program such as the Affordable Care Act. It’s also labor-intensive; Botero’s group, Enroll America, expects to talk to each person seven to eight times to encourage enrollment in a health plan.

“Obviously, we’ve got to find the uninsured, but we’ve got plenty of examples of finding the uninsured and letting them slip away,” said Stan Dorn, a senior fellow at the Urban Institute and a supporter of the law. He said such campaigns work only if the volunteers take the extra step of filling out the people’s forms — an even more laborious role that Enroll America does not plan to undertake.

Enroll America and other groups, including insurance companies and state health departments, are nevertheless taking their pitches directly to people’s doorsteps.