When Central Valley Congressman Jeff Denham last week faced a crowd of voters furious with his vote to kill the Affordable Care Act, he — like many Republicans around the country — might have wondered where all the energized protesters came from.

Some of them were inspired by Ezra Levin and Leah Greenberg, two 30-year-old former congressional staffers who founded Indivisible, an anti-Trump group. In the last five months, a how-to-resist-Trump guide published by the D.C. husband-and-wife duo has gone viral and blossomed into a bona fide grass-roots movement. But even as Indivisible has energized activists around the country and added a shot of drama to town hall meetings, it also has ruffled feathers, including those of some liberal Bay Area politicians.

Levin and Greenberg are hoping to spark a progressive version of the Tea Party movement, which led to conservative protesters hounding members of Congress for supporting former President Barack Obama’s signature health care law. The two had seen the power of the Tea Party firsthand: Greenberg worked for former Congressman Tom Perriello, a Virginia Democrat who lost his seat in the 2010 Republican wave.

“We know what works,” Levin, who talks quickly and has a face full of freckles, said during a recent interview in the Bay Area. “Putting aside their racism and their violence, the Tea Party was smart on strategy.”

Along with friends who had worked in Congress, Levin and Greenberg wrote up a Google Doc distilling what they had learned about advocacy. Their advice: Go to congressional town hall meetings, pressure your representatives to publicly oppose President Donald Trump and his agenda, and keep calling them and showing up at their office until they agree to speak out against the president.

“Every single member of Congress cares more about their own re-election than they care about anything that the Trump administration wants to get done,” Levin said.

Levin tweeted the document — which he says still had “a lot of typos” — from his personal account to 650 followers on Dec. 14.

2/x: To help, former congressional staff drafted this guide, drawing lessons from how the Tea Party stopped Obama. https://t.co/YrNWX6c4s0 — Ezra 🌊 Levin (@ezralevin) December 15, 2016

Within a few days, the guide racked up hundreds of thousands of views and was shared by prominent politicos such as Robert Reich, the former secretary of labor, and George Takei, the “Star Trek” actor and Trump critic. “It was way more exposure than we ever expected to get,” Greenberg said.

So Levin and Greenberg built a website and encouraged people to make their own groups. It’s not very formal — with a few clicks, anyone can create an Indivisible group in their own town or neighborhood and invite other people to events. So far, there are at least two groups in every congressional district in the country, and more than 900 groups in California. Activists around the country have followed the guide’s advice, packing town hall meetings and haranguing members of Congress.

It’s attracted people like Emily Morris, 27, a San Mateo woman who works for a nonprofit and was never politically involved before she joined Indivisible San Francisco in January. “The election turned my world completely upside down,” she said.

Morris said meeting other outraged Democrats energized her. “Indivisible was this kind of antidote to despair,” she said.

Sherry Bebitch Jeffe, a longtime political analyst at the University of Southern California, said Indivisible was smart to demand town hall meetings as a tool to put pressure on representatives.

“We didn’t used to have town hall meetings,” she said. “They are being demanded by constituents now, to great effect.”

She noted that a desire for ideological purity from Tea Party activists led to several 2010 Senate races in which conservative nominees lost races that moderate Republicans likely would have won.

Levin said it was important for members of Congress to oppose Trump at every turn. While some Democrats had talked about cutting deals with Trump — on an infrastructure bill, for example — “if you don’t resist, you’re going to have a Muslim refugee ban, and you might build a few roads,” he said.

Indivisible’s activities haven’t gone over well with congressional Republicans. Rep. Dana Rohrabacher, R-Huntington Beach, called members of the group “enemies of American self-government and democracy” after protesters with Indivisible got into a scuffle with his staff members in February.

“Though the protesters think of themselves as idealists, they engaged in political thuggery, pure and simple,” Rohrabacher said.

Indivisible groups have also put pressure on Democrats and liberals. In February, the Indivisible East Bay group requested a meeting with California Sen. Dianne Feinstein, and held an Oakland event with an empty chair to represent her when she couldn’t make it. Members of the group also showed up at a fundraiser she held in Los Angeles.

Finally, Feinstein agreed to hold public town halls. In two meetings in San Francisco and Los Angeles last month, hundreds of people showed up, booing, jeering and grilling her on why she wasn’t doing more to oppose Trump.

In Contra Costa County, members of Indivisible once arrived unannounced at Rep. Mark DeSaulnier’s district office and demanded to meet with him — even though he was in Washington at the time.

DeSaulnier, D-Concord, said in a recent interview that he thought the Indivisible guide unfairly portrayed members of Congress as “Pavlov’s dog” or “shameless scum.” Still, DeSaulnier said he’s enjoyed meetings with local Indivisible members. “I’m really pleasantly surprised and really happy that they want to stay engaged in a way that is constructive and respectful,” he said.

Rep. Zoe Lofgren, D-San Jose, had never heard of Indivisible when a group of 50 members met with her earlier this year. Now she’s seeing the busiest town hall meetings of her 22-year congressional career, she said.

“None of these people I’ve ever seen before in Democratic Party politics,” Lofgren said. “They want to do something.”

The biggest challenge now for Indivisible is how to keep people energized for the long haul. The group has been sending its members training documents, like scripts for phone calls with Republicans who voted to repeal and replace the Affordable Care Act, or a briefing on why groups should demand an independent investigation into Russian influence over U.S. elections.

Levin and Greenberg have quit their day jobs to work on Indivisible full-time and hired 16 other staff members with funding from donations. Going forward, they’re planning to endorse specific congressional candidates, but they say they’ll let the local grass-roots groups lead the movement.

As they wrapped up an interview in a San Jose coffee shop, the guy at the next table — Andre da Vitoria, a 25-year-old recent grad with a man bun — leaned over to say he’d overheard their conversation with a reporter.

Noting that he’d just signed up to do phone calls for his local Indivisible group, he asked Levin: “Can I shake your hand?”