Colorado state Sen. Evie Hudak, the latest Democrat to be swept up in the state’s recall brushfire, is fighting back with a cash infusion from Washington, D.C.

Two pro-Hudak issue committees have raised $50,428 since Oct. 23 to fight the recall effort, with $30,000 coming from Environmental Majority, a Washington-based political action committee, according to campaign finance reports.

That war chest — more than twice what recallers have raised in their push to place the Democrat on the recall ballot — has allowed the Hudak campaign to blanket her suburban Jefferson County district with door-hangers, robocalls and yard signs urging residents not to sign the recall petitions.

Pro-Hudak protesters, some of whom are affiliated with labor unions, have also waged an aggressive street campaign to discourage residents from signing, in some cases using bullhorns, tambourines and other noisemakers to scare off voters at sign-and-drive sites.

“We had a gentleman, a World War II veteran, who couldn’t walk very well but made his way to the sign-and-drive at the King Soopers, and they were honking horns and shaking tambourines in his ears,” said Joe Neville, political director of Rocky Mountain Gun Owners, which is supporting the recall.

Mike McAlpine, an organizer of Recall Hudak Too, says the robocalls have put a damper on signature-gathering. The committee needs to submit about 18,900 valid signatures by Dec. 3 in order to force a recall election.

“This is a community alert for Arvada and Westminster from the Democracy Defense Fund,” says a robocall message posted on several media websites. “Paid signature-gatherers who have not gone through a criminal background check could be in Westminster and Arvada this week asking for signatures on a recall petition. Do not sign this petition.”

Volunteers at the Recall Hudak Too storefront office in Arvada said the robocalls sound like a reverse 911 call that would be issued by police in the event of an emergency.

“The robocalls are affecting people such as seniors who mostly stay at home,” said Mr. McAlpine. “It sounds like an official public-service announcement, and they’re very concerned about it.”

Recall Hudak Too has raised $23,296 from nearly 500 donors, most of them Colorado residents contributing $100 or less. So far the group is relying on its army of volunteers to collect signatures, but Mr. McAlpine said they may soon have to turn to paid signature-gatherers.

“We’re right on the edge of committing to that,” said Mr. McAlpine. “We’re in this to win.”

The Hudak recall comes as the latest backlash to the Democrat-controlled state legislature’s sweeping gun-control bills, signed into law by Gov. John Hickenlooper in March. Voters recalled Senate President John Morse of Colorado Springs and state Sen. Angela Giron of Pueblo in the state’s historic Sept. 10 special election.

In some respects, Mrs. Hudak should be an easier target, given that her district is evenly split between Democrats and Republicans. She barely won her seat in 2012, pulling out a 342-vote victory in a race that also featured a Libertarian Party candidate.

On the other hand, the petition hurdle is more than 6,000 signatures higher than it was in the previous recalls. In addition, Democrats who initially dismissed the Giron and Morse recalls are not about to make the same mistake twice.

On a sunny Saturday afternoon, dozens of advocates on both sides waved signs at passing cars along Wadsworth Boulevard, Arvada’s main drag. Interspersed between the bright yellow “Recall Hudak” signs were “No Recall” and “Decline to Sign” placards.

“I support what I believe is right. I’m a part of the labor movement and that’s all I’ll tell you,” said a young man with an anti-recall sign and a “Sheet Metal Workers” T-shirt who declined to give his name.

Nearby, Audrey Kline, a recent Arvada West High School graduate who held a homemade “Gun Owners for Hudak” sign, said that Mrs. Hudak’s votes in favor of three gun-control bills had no impact on her gun rights.

“In fact, I feel safer because the bills were passed,” said Ms. Kline. “This is not about guns. It’s about a majority in the Senate, and Evie’s been one of the most supportive people in the Senate of what I believe in.”

Democrats hold an 18 to 17 majority in the state Senate, which would flip if Mrs. Hudak were recalled and succeeded by a Republican. Analysts agree that Democrats would never allow that, and would push instead for Mrs. Hudak to resign and be replaced by another Democrat if the recall petitions qualify.

Even if Mrs. Hudak were to resign, those in favor of the recall said they hoped the campaign would send a message to the state legislature, which has been described as the most liberal in state history.

“I’m a third-generation Coloradoan, and this isn’t the Colorado I grew up in,” said Bob Kagohara, wearing a pro-Second Amendment T-shirt and holding a “Recall Hudak” sign. “People from California have moved in and turned it into a Bloomberg state.”

He was referring to New York City Mayor Michael R. Bloomberg, whose group Mayors Against Illegal Guns lobbied for the Colorado gun-control measures.

“Because of the John Morse and Angela Giron recalls, that got a lot of interest going in this district,” said Mr. Kagohara. “So there’s more interest, but at the same time, she’s got her people organized, too.”