WASHINGTON — More than three-quarters of visitors to the federal ObamaCare Web site who were eligible for insurance reported being healthy, a new survey shows.

That could be good news for President Obama’s sweeping health-care law, which needs a large number of young and healthy people paying into the system to help cover the cost of new universal benefits.

The survey by New York-based Commonwealth Fund found that the largest group of visitors — 41 percent — was young adults ages 19 to 34, who are the prized demographic needed to make the new national health plan work.