In the weeks after Donald Trump won last year's presidential election and Republicans kept control of Congress, Sarah Dohl, with a of friends and former Capitol Hill colleagues, wanted Americans — mostly distraught Democrats — to know that their voices could still be heard.

Not expecting much, they published online a 26-page document in mid-December, outlining a succinct idea: resist.

Its title, "Indivisible: A Practical Guide for Resisting the Trump Agenda," quickly drew interest. George Takei, the actor who starred in the television series "Star Trek," posted a link to it on Twitter. So did former Labor Secretary Robert Reich, who worked in the Clinton administration.

"We just had no idea it would turn into this huge movement," Dohl said Saturday. "We thought our moms might read it."

What at first started with a small group of young progressives batting around ideas on how to move forward under a Trump administration has blossomed into a national movement, known as Indivisible. The mission centers on grass-roots advocacy targeting members of Congress inclined to work with the new administration and those who, in Indivisible's view, don't do enough to oppose it.

In keeping with the loose structure of other movements such as Black Lives Matter, Indivisible isn't a hierarchical organization with a national headquarters and local chapters. Instead, it's a collection of groups committed to employing tactics and operating on principles shared by Indivisible's founders online.

Early on, the focus was attacking Republican efforts to repeal the Affordable Care Act.

Members of the movement have caused representatives to flee town halls and, at times, cancel public events altogether. They've corralled constituents, visited district offices and made phone calls en masse demanding answers.

Not all people who flooded congressional town halls in recent weeks were part of — or had even heard of — Indivisible. But many were.

"Every member of Congress cares about how their constituents view them and the narrative being formed in their districts," said Dohl, who has held several jobs on Capitol Hill, including communications director for Rep. Lloyd Doggett, D-Texas. "And we're not just focused on Republicans. This is about Democrats standing up and having a spine and pushing back against Trump and Republicans."

A chapter in the published Indivisible guide is titled, "How your member of Congress thinks and how to use that to save Democracy." It offers a simple point:

"To influence your own Member of Congress (MoC), you have to understand one thing: every House member runs for office every two years and every Senator runs for election every six years. Functionally speaking, MoCs are always either running for office or getting ready for their next election — a fact that shapes everything they do."

The strategy, said Dohl, echoes the tea party movement that sprang up in 2009. At the time, President Barack Obama's efforts to pass the Affordable Care Act caused a conservative uproar. Images of constituents, angered by the legislation and jabbing fingers in lawmakers' faces, filled television screens and front pages nationwide. The next election cycle, Democrats, who at the time had controlled both chambers of Congress, lost the House.

Now, members of the movement hope it's the reverse.

"We're seeing people who have never been involved in politics now motivated to speak up," said Ezra Levin, who came up with the idea for the online guide and is now president of Indivisible Guide, which recently registered as nonprofit group. He worked with Dohl on Capitol Hill in 2009, during the rise of the tea party.

On Saturday, the two celebrated the Repbublican collapse on health care. A day earlier, House Speaker Paul Ryan pulled a bill that would have repealed and replaced the Affordable Care Act because it did not have enough support. Many in the Freedom Caucus, among the most conservative members of Congress, thought the bill did not dismantle the law enough. Democrats and moderate Republicans thought it went too far.

Levin credits Indivisible groups for influencing moderates such as Rep. Barbara Comstock, a Republican who represents a swing district in Virginia.

For weeks, Comstock declined requests from constituents — some of whom are associated with Indivisible — for an in-person town hall. Her Capitol Hill and district offices were also flooded with phone calls from constituents seeking more access to her.

On Friday, hours before the bill was pulled, Comstock said she would not support it.

"This is setting the tone for members of Congress to know that constituents are paying attention," Levin said. "And they're not going to stop. This is going forward for months and years."

Laynette Evans, a career coach and resume writer, is among the early organizers of Indivisible Reno.

The Reno group has about 1,100 Facebook members and has met a few of times to talk about how to get their representatives at all levels of government — Democrats and Republicans alike — to hear them out on issues including health care and immigration.

"It's putting politicians on notice," said Evans, a Democrat. "With the election of Donald Trump, I think more people are becoming engaged in politics and how our country is being governed."

In January, a day after Trump's inauguration, millions of people joined women's marches nationwide. As protests of Trump have ensued, several states have sought to pass legislation that would discourage or criminalize protest. And Trump has described protesters — those at town halls or marching in the streets — as paid professionals who specialize in disrupting Republicans.

After the failure to repeal the Affordable Care Act, Trump has indicated he's ready to move on to other issues, such as tax reform.

Whatever the proposal, Trump and Republicans will probably face Indivisible, Levin said.

The resistance is not going away, he said.