Within hours of the networks declaring on Nov. 9 that Donald Trump would be the next president, officials at the health care advocacy group Families USA decided to convene a nationwide conference call of activists and interest groups. The subject: saving Obamacare from repeal.

They circulated an invitation email at about noon for a scheduled call at 3 p.m. ― not a lot of lead time, particularly with so many of the Affordable Care Act’s most passionate defenders in varying states of shock and sadness over the election results.

But more than 1,000 people called in, according to Ron Pollack, president of Families USA. “The response was tremendous,” he said. And since then, he says, firm plans have started to take shape.

Several groups have formed a network they are tentatively calling “The Coalition to Keep America Covered.” Through a combination of storytelling, grassroots organizing and advocacy to individual members of Congress, the group’s goal will be to protect the insurance coverage that Republicans now threaten ― starting with the more than 20 million Americans who now depend on Obamacare.

Staving off repeal won’t be easy, obviously. Republicans have been pledging to wipe away President Barack Obama’s signature domestic policy ever since 2010, when he signed it into law. And with control of Congress, all Republicans have needed is a president who has pledged to achieve the same goal.

There’s also a chance that Republicans will push further by trying to privatize Medicare and turning Medicaid over to the states, as House Speaker Paul Ryan pledged again on Sunday to do.

But rolling back or eliminating these programs may prove more difficult than Republicans and their allies imagine ― even when it comes to Obamacare, a program that consistently proves unpopular in the polls.

Obamacare reorganized the insurance market for people buying coverage on their own, imposing new rules ― like prohibitions on insurers denying coverage because of pre-existing conditions and requirements that all policies include comprehensive benefits. The law also created “exchanges,” through which consumers can get tax credits, available based on income, that discount premiums.

In addition, Obamacare provided states with money to expand Medicaid dramatically, so that it’s available to all people with incomes below or just above the poverty line. Thirty-one states plus the District of Columbia have done so, and the list includes several whose narrow margins gave Trump a majority in the electoral college ― among them, Michigan, Ohio, and Pennsylvania

The changes to the insurance market were disruptive, and left a significant portion of consumers, particularly those who don’t qualify for tax credits and buy directly from insurers rather than through the exchanges, feeling like they are paying too much for policies that cover too little. Many insurers have taken serious losses, because they’re not attracting enough healthy customers to offset the costs of the sick.

But while those problems have received the most press coverage over the last few years, fueling a political backlash, they may not reflect the reality of Obamacare as most of its beneficiaries experience it.

Surveys suggest that the vast majority of people who have bought Obamacare through the exchanges or signed up for Medicaid are pleased with the coverage and what they are paying for it. By and large, these are people who struggled to pay for insurance previously, or had no access to comprehensive coverage because of their medical histories or risk of getting sick. Without the law’s protections and funding in place, many would go back to being uninsured again ― a point that the Congressional Budget Office recently confirmed, when it predicted that outright repeal of the law would increase the number of uninsured Americans by 22 million.

Of course, both Trump and the Republicans have promised to replace Obamacare with an alternative, implying they can provide equivalent or better benefits with lower costs and less hassle ― “great health care for less money,” as Trump said in his recent “60 Minutes” interview.

But the schemes that conservatives have proposed, and that Republicans have suggested they might support, would likely result in either a significant reduction in the number of people with insurance, a significant reduction in what insurance covers, or a mix of the two. (A very rough Commonwealth Fund analysis of the Trump Obamacare “replacement,” for example, concluded that the end result would be something like 20 million more uninsured.)

In an interview, Pollack said that a main goal of groups like his will be to shine a spotlight on the impact repeal would have. One way to do that, he said, would be by focussing on the financial or medical struggles individual people would face if they were to lose coverage ― and to make sure policymakers hear their stories.

“Once you start talking about repealing the ACA, given what Republicans want to do and what they don’t want to do, it’s going to be very difficult to occur in a way that doesn’t cut coverage for millions of people,” Pollack said. “So our job is to make sure people understand the human toll that would occur.”

Pollack understands better than most people the enormous political pressure to eliminate the law, and how that will weigh on Republicans who have made repeal one of their very top priorities.

Pollack was among a handful of interest group leaders who spent the years leading up to 2009 building a coalition in favor of reform ― and then spent the first 14 months of Obama’s Administration fighting desperately, and ultimately successfully, to hold that coalition together in the face of conservative opposition.

That was a tough fight, in part because the benefits of Obamacare were still entirely hypothetical. That’s not true anymore, and it’s the one big advantage that Pollack feels he and his allies have this time around ― despite the daunting political circumstances.

“We obviously believe that it’s much harder to take something away ― especially if it’s valued and constitutes a real life line ― than it is to withhold something people didn’t have before,” he said.