This article is part of the Opinion Today newsletter. You can sign up here to receive more briefings and a guide to the section daily in your inbox.

Since Obamacare became law, it’s been subject to one challenge after another. Some challenges have truly been existential, like the 2012 Supreme Court case and this year’s repeal effort in Congress. Others have had the potential to do damage without undermining the entire law.

President Trump’s actions last week are in the second category.

“This stuff is really bad, but it’s not nearly as bad as repeal,” as Aviva Aron-Dine, of the Center on Budget and Policy Priorities, told me. Jonathan Cohn, of HuffPost, has made the same point: “The damage is not catastrophic. But it is real and it will linger.”

What can you do about this? That’s a good question to ask, since citizen activism played a crucial role in defeating the repeal efforts this year. My column today offers a guide for people who believe in decent medical care and want to defend it against Trump.