President Obama urged a group of young activists Wednesday not to give up on promoting his signature health-care law, as enrollment picked up on

Roughly 27,000 Americans signed up for insurance on the federal exchange on Tuesday, according to internal figures, bringing the site’s three-day enrollment total to 56,000. That figure is more than double the number who enrolled online in the entire month of October, which was almost 27,000.

Buoyed by the Web site’s improved performance, Obama and his aides have been touting the importance of signing up for plans before Dec. 23, the deadline for obtaining insurance scheduled to start Jan. 1.

Obama told the group at the White House Youth Summit, which was designed to mobilize support for the health law, that he needed them “to spread the word about how the Affordable Care Act really works, what its benefits are, what its protections are and, most importantly, how people can sign up.”

“Look, you know, I do remember what it’s like being 27 or 28, and aside from the occasional basketball injury, you know, most of the time I kind of felt like I had nothing to worry about,” the president said. “Of course that’s what most people think until they have something to worry about, but at that point, oftentimes it’s too late.”

Many young people remain reluctant to buy a health plan on the state and federal exchanges. A new poll by the Harvard Institute of Politics found that 29 percent of young, uninsured Americans say they are leaning toward enrolling, with 41 percent saying it’s a 50-50 proposition.

Young Invincibles executive director Aaron Smith, whose group is working to get young people insured, said the fact that the summit’s attendees included DJs and young entrepreneurs shows that the White House is looking for messengers “who are not in the political arena, but have an entry point into young people and know how to communicate to young people.”

Smith said that while many young Americans remain undecided about whether they will sign up for insurance, some don’t know about the law’s central provisions, such as guaranteed coverage for people with preexisting medical conditions.

Obama compared the push to expand health-care coverage to the civil rights, women’s and labor movements, telling the group of young supporters gathered in the South Court Auditorium, “I hope you haven’t been discouraged by how hard it’s been, because stuff that’s worth it is always hard. . . . You know, it’s never been easy for us to change how we do business in this country.”

The president also took aim at conservative groups campaigning against the health-care law, warning that if any of their members were to become sick or get in an accident, “The people who are running those ads, they’re not going to pay for your illness. You’re going to pay for it or your family is going to pay for it.”

The White House’s renewed push for the law came as received an 80 percent increase in visitors, according to Centers for Medicare and Medicaid Services spokeswoman Julie Bataille.

Bataille declined to release detailed recent enrollment figures, which under the agency’s definition include any individual who has successfully signed up for a plan.

“We are still scrubbing those numbers right now,” she said in a phone briefing with reporters, adding that the agency will release new enrollment numbers by the middle of the month. “We expect our numbers to increase, given the technical improvements to the Web site.”

The three-day total of 56,000 enrollees, while short of the pace needed to reach the administration’s target of 7 million by March 31, shows that the federal health insurance marketplace is working much more smoothly than it was at its Oct. 1 launch.

Before last weekend, the previous daily high was more than 9,600 on Nov. 26, according to another government official who declined to be identified in order to discuss the site’s operations.