(CNN) Rep. Jason Chaffetz blamed his harsh reception at a recent town hall on " a paid attempt to bully and intimidate ." White House press secretary Sean Spicer called anti-Donald Trump marches and protests " a very paid, AstroTurf-type movement ."

But the protesters say they're fighting Republicans for free.

As GOP lawmakers prepare for a week of raucous town halls during a late-February congressional recess, some are dismissing the massive crowds, casting them as the efforts of well-funded liberal groups paying protesters to pose as members of a grassroots movement.

They have not offered evidence to support the claim, though -- and Democratic organizations say they're just racing to keep up with what they insist is an organic uprising fueled by opposition to Trump.

At Chaffetz's event, attendees -- mostly progressives -- cited a long list of ways they'd heard it was taking place. Some said they'd read it in the Salt Lake Tribune, others via word of mouth. Several said they'd gotten notices from Chaffetz's office.

Most frequently, attendees pointed to Utah's chapter of Indivisible, a loosely organized, weeks-old group with hundreds of regional affiliates.

Leah Greenberg, one of Indivisible's five co-founders, said the organization started as a Google Doc offering advice for protesters -- instructing them to focus their efforts on their local lawmakers, rather than figures like the House speaker, and telling them that "you have the most leverage as a constituent when you are focusing on the issues that are on your member of Congress's mind at one time."

The protest guide, which they expected to go without much notice, gained immediate traction.

The five co-founders and volunteers from their personal networks of progressive friends and fellow congressional staffers launched a website and social media accounts, and then added those who formed local groups based on the Indivisible protest guide's principles into a database.

"That's all that we are doing," Greenberg said. "It's just a platform for people finding other people that are interested in pursuing it."

Three weeks ago, Indivisible began accepting donations. Needing someone to manage its website, email list and social media accounts, the organization hired its first employee this week.

Greenberg said they've never paid anyone for anything. Even Indivisible's one employee hasn't yet received a check.

"At every stage in this process, we have been surprised by the amount of enthusiasm and energy and activity that is happening, and we've just been trying to keep up with it," she said.

Much like well-funded conservative organizations -- some backed by the Koch brothers -- stepped in to build an infrastructure around the tea party in 2009, some Democratic organizations are also attempting to train and channel the protesters.

A broad coalition of groups including Organizing For Action, the SEIU, MoveOn.org and the Center for American Progress have been working to help with grassroots organizing around GOP town halls.

Organizing for Action, the group formed from former President Barack Obama's campaign organization, has 14 professional organizers, for example, who are involved in teaching local activists skills to effectively vocalize opposition to the GOP's top agenda items -- particularly the repeal of Obamacare.

OFA has held six webinars and training calls so far -- with more than 25,000 registered participants. One call was for Indivisible members. OFA volunteers have also attended several recent Republican town halls.

"The grassroots energy that's out there right now is palpable. OFA is constantly hearing from volunteers who are excited to report about events they're organizing around and all of the new people that want to get involved," said OFA communications director Jesse Lehrich. "We're just doing the best job we can to be resources to constituents who want to make their voices heard -- whether that means letting them know when their members of Congress are holding town halls, providing them with an online tool to call their senators, or training them on best practices for having respectful and productive interactions."

Planned Parenthood has also seen an explosion of interest in activism from its members, and is planning more than 100 events for next week during the congressional recess.

The group "Together We Will," which claims to have around 350,000 members across the country that have been targeting GOP town halls, has no funding source, the group's founding director Marilyn Lucey told CNN.

"The news has been centered around grassroots people being paid to show up at town halls and protests -- that cannot be further from the truth," Lucey said. "'Together We Will' and other grassroots organizations are running complete on energy and emotion and commitment. There are no dollars being exchanged."

The group has sold t-shirts to fund "basic costs," Lucey said, but there are no salaries or stipends. "Everyone is a volunteer," she said.

Origins of Chaffetz's claims

Chaffetz told the Deseret News after Thursday's town hall that he believed those attending were paid, out-of-state rabble-rousers.

"You could see it online a couple days before, a concerted effort in part to just cause chaos," he said. "Democrats are in disbelief that they have nothing but flailing and screaming to deal with this."

Asked for evidence to support his claims, Chaffetz spokeswoman MJ Henshaw on Monday pointed to tweets from the Cottonwood Heights Police Department.

The local police office tweeted: "Armed/masked protesters asked crowd to rush the cops @ Chaffetz rally. Crowd defended officers and there were no arrests. Lt Bartlett PIO."

Then, it wrote: "We spoke with people from all over including outside of Utah who attend Rep Chaffetz meeting. Thanks for being respectful to Police Officers."

Armed/masked protesters asked crowd to rush the cops @ Chaffetz rally. Crowd defended officers and there were no arrests. Lt Bartlett PIO — CH Police (@CHPolice) February 12, 2017

We spoke with people from all over including outside of Utah who attend Rep Chaffetz meeting. Thanks for being respectful to Police Officers — CH Police (@CHPolice) February 12, 2017

Dan Bartlett, the police lieutenant responsible for those tweets, told CNN Monday that two men wearing handguns on their hips (Utah is an open-carry state) and bandanas over their faces were "yelling at the crowd to rush the cops when we had closed the front door to the school when it reached occupancy."

But the crowd of hundreds of anti-Chaffetz protesters actually stepped in and defended police, Bartlett said.

"The crowd was great with us," he said.

Inside the town hall, CNN found one couple that had driven from Arizona to participate -- but dozens of others all said they were from Utah, and spoke of local issues that concerned them.

Asked about the tweet indicating some had come from out of state, Bartlett said, "It wasn't a large majority or anything like that. We just talked to a few people who had come from out of town."

Told that CNN had found most were Utahns, he said, "Oh yeah, absolutely."

Attendees say they weren't paid

After the Chaffetz town hall Thursday night, Dr. Kathie Allen called herself a "newly-formed activist" and said she's considering running as a Democrat against Chaffetz in 2018. She said she's sought training from Emily's List and the science-focused group 314 Action, both of which are attempting to recruit more female candidates for office.

The town hall -- the first one Chaffetz hosted that Allen had ever attended -- was, she said, "democracy in action."

Amy Crawford, 41, said it was the first time since she'd moved to Utah six years ago attending a town hall. "A lot of my friends who were not politically engaged before are now finding themselves politically engaged -- they feel it's their civil duty," she said.

Sarah Taylor, 33, an editor in Provo, said Chaffetz's town hall was "the first one I've ever been to." She and other attendees said they'd never been politically active in the past. "Not even close," Taylor said.

Kaz Weida, a 41-year-old copywriter who lives about a mile from the location of Thursday night's town hall, said she heard about the event through two activist groups -- Utah Women Unite and Our Utah.

Lindsey Corum and her husband Dan Ransom got invites from Chaffetz's office, Corum said, and brought hand-made signs.

"I do not know anyone that was paid to attend. In fact, people were excited to attend free of charge, to have their voices heard," she said. "Salt Lake County is effectively gerrymandered and the people in this part of his district are angry that their voice has been largely silenced by the conservative majority in this state."

Chaffetz stands by his unsubstantiated claims

Henshaw, Chaffetz's spokeswoman, said Monday that the Utah Republican stands by his claims of paid protesters.

But she pointed to comments Chaffetz made to the Salt Lake Tribune , in which he took a different tone.

"The overwhelming majority of people there were Utahns; they weren't paid," Chaffetz told the newspaper. "But I do believe there was a concerted, national effort, some of which was paid, to get people there to cause a problem."

Some Republicans are acknowledging that the intensity they face at town halls is largely local.

Rep. Gus Bilirakis, R-Florida, held his second contentious town hall in two weekends on Saturday, with a crowd that police estimated at 250 on hand, largely to urge him not to repeal Obamacare.

Unlike Chaffetz, Bilirakis made no claims that attendees came from out of state.

"I think probably the majority of the people in the room were my constituents," he told CNN.