Last night—and I kind of can’t believe I’m typing these words—the former host of The Man Show put the United States Congress on notice.

“We can't let them do this to our children, our senior citizens, our veterans, or to any of us," Jimmy Kimmel declared during the opening monologue of his late-night show, decrying the latest Obamacare repeal bill. Earlier this summer, Republican Senator Bill Cassidy had coined the phrase “Jimmy Kimmel test,” promising that any Republican health care plan would cover children such as Kimmel’s young son, who was born with a heart condition. It’s a promise the senator now likely regrets.

“There’s a new Jimmy Kimmel test for you,” the ABC host announced. “It’s called the lie detector test.”

It’s far too soon to declare the latest incarnation of Trumpcare defeated. (Seriously, if you’re reading this, stop reading and call your senator.) But Kimmel made it clear that Congress won’t be able to upend one-sixth of the economy in secret, and that they’ll be held accountable for whatever happens next.

No less important, however, last night’s monologue is a blueprint for famous people who hope to get involved in politics. Celebrity activism—particularly the left-leaning kind—has never been more risky or difficult. But by following Kimmel’s example, progressives can still harness star power for social change.

From 2011-2016, I wrote speeches and jokes for Barack Obama, where I got to be part of an administration that married entertainment and activism more effectively than ever before. (In my new book I write about how Between Two Ferns helped save the Affordable Care Act, and how “Luther, Obama’s Anger Translator” helped the president deliver a deadly serious message about climate change.)

But in last year’s election, celebrity activism hit a ceiling. A famous person’s endorsement is no longer enough to sway public opinion or send people to the polls. Americans are understandably skeptical of wealthy stars telling them which candidate to vote for. And thanks to conservative media, the backlash to “Hollywood liberals” often outweighs any benefit that comes with their support.

It’s worth looking at how Kimmel threaded the needle.

First, he spoke to his unique personal experience. Jimmy Kimmel’s probably not the right person to tell us about infrastructure funding, or border security, or gun violence. But as the father of a child with a potential life-threatening condition, no one can claim he has no business wading in on the healthcare debate. This is also what made Aziz Ansari’s op-ed on immigration or Lena Waithe’s Emmy acceptance speech about diversity and identity, so effective. By addressing something specific and personal, celebrities can avoid being dismissed as dilettantes.

Second, Kimmel chose an issue where the primary problem was a lack of attention. If Graham-Cassidy was wildly popular, I doubt even the sharpest monologue would do much to derail it. But Graham-Cassidy is wildly unpopular—the bill’s sponsors best hope to sneak it through while we talk about Trump’s bizarre “Rocket Man” speech. The conventional wisdom is that celebrities have a megaphone, but it would be more accurate to say they have a spotlight. They can’t always shape our opinions, but they can demand our attention. And sometimes, that’s enough.

Finally, Kimmel directly tied his advocacy to action. When entertainers take a stand, it’s often cathartic and inspiring, but it rarely leaves lawmakers quaking in their boots. But last night’s monologue wasn’t just about right and wrong. It was about what to do next. By putting up the number for the Senate switchboard, and directly asking voters to call, he magnified his impact. Senators don’t really care if they get a talking-to from a celebrity—but they absolutely care about not losing their jobs.

Just nine months into the Trump era, Americans are coming out of the woodwork to oppose Donald Trump and the party that supports him. Entertainers want to play their part, and that’s a good thing. But if there’s one thing I learned at the White House, is that politics requires not just a passion, but a strategy.

By following a kind of “Jimmy Kimmel test” for activism, celebrities can turn fame into a powerful force for change.