Patti Seno registered for Rep. Mike Coffman’s town hall meeting expecting to ask him about health care. The deadly mass shooting at a Florida high school changed all that.

In a high school auditorium here, amid a suburban landscape scarred by the acts of mass gun violence in the nearby towns of Littleton and Aurora, Seno delivered a stern message to the five-term Republican, whose response, at times, was met with jeers.

“It took children to shake me from my comfort zone to come forward to say: Enough is enough,” said the 53-year-old benefits administrator, referring to the students who have spoken out after a troubled ex-student, the alleged shooter, killed 17 people inside a Florida high school last week.

“There is no way a 19-year-old, and a 19-year-old with the problems this young man had, who can’t even buy alcohol, should be able to buy a weapon of mass destruction,” she told Coffman, pressing him to support age limits on gun purchases and adding, “An avalanche is coming to Washington, sir, and it is going to be led by our children.”

Whatever fresh public momentum exists for new gun legislation in Congress, Coffman felt it Tuesday night, with roughly half of the questioners he faced during the hour-long event pushing him to do something — anything — to stem the bloodshed in American schools with a rowdy, frustrated crowd egging them on.

Coffman, for the most part, did not give them the answers they were seeking. He said he would “look at” raising age limits for gun purchases. He opened the door, with many caveats, for expanding the circumstances where potentially dangerous individuals might have their gun-owning rights curtailed. But he was on more comfortable ground calling for improvements to school security and mental health care — and not impeding what he called “responsible gun ownership.”

Rep. Mike Coffman (R-Colo.) talks to reporters prior to a town hall meeting Tuesday night. He faced questions on guns and immigration among other issues. (David Zalubowski/AP)

“We live in an imperfect world,” he told one questioner as the crowd erupted in jeers. “There is no way that you can say, no matter what laws you pass, that bad things are not going to happen.”

Sparking another uproar, he mused, “Why do we give more protection for any federal building than we do for a school? . . . Force has to be met with force.”

Since 2012 — when shooter James Holmes killed 12 and injured 70 inside an Aurora movie theater — Coffman has been a walking and talking lesson in the limits of anti-gun politics.

That year, thanks to new district lines that made Colorado’s 6th congressional district more suburban and much more competitive, Democrats put unseating Coffman near the top of their national priority list. That year, and every election year since, a Democratic candidate has run against Coffman with strong national party support and a campaign platform calling for stronger gun laws, only to lose every time.

Some of the reasons Coffman has survived in a moderate and diverse suburban district were on display as he fielded the other half of the questions he heard Tuesday — many of them concerning immigration, particularly protections for young immigrants brought to the United States as children who now face deportation due to President Trump’s cancellation of the Deferred Action for Childhood Arrivals (DACA) program.

Completing a pivot from his earlier hard-line immigration views, Coffman has been a prominent Republican voice calling for “dreamers” to be protected. He won applause from a skeptical crowd Tuesday when he said that, if Congress does not act by next month, he would dust off his effort to force action on a bill extending DACA for three years — over the objections of House Republican leaders.

GOP party strategists argue Coffman has forged a unique and durable bond with voters in his swing district and see no reason 2018 will be different from the past three elections.

“Mike Coffman is as formidable as they come, and you would be hard-pressed to find anyone who’s done more for [the 6th district] than he has,” said Jesse Hunt, a spokesman for the National Republican Congressional Committee.

Democrats believe Coffman has new reasons to sweat this year: One, of course, is Trump, whose unpopularity threatens to drag down GOP incumbents across the country — especially one running in a district Democrat Hillary Clinton won by nine points. They also believe Coffman will have to answer for a voting record that, they say, belies his image as a independent willing to buck the GOP line.

Over the past year, he has voted for the Republican health care and tax bills and has supported two gun rights measures — one forcing states to recognize concealed-carry permits from other states, and one overturning an Obama administration regulation that could prevent some mentally disabled people from purchasing guns.

National Democratic party officials also think they have a better challenger this year. After three straight state legislators failed to unseat Coffman, they have thrown their support behind Jason Crow, a lawyer and former Army Ranger officer making his first run for office.

“What the Donald Trump presidency has done is it’s forced him to take the votes on his politics,” said Crow, who leads in fundraising among several Democratic candidates but must win a June 23 primary. “After a year of that he’s got a 95 percent voting record with this administration and with [Speaker] Paul Ryan. That’s not somebody standing up to anybody.”

Crow is backing several changes to gun laws, ranging from eliminating the congressional prohibition on federal gun violence research to mandating universal background checks to banning “military-style” weapons like the AR-15 rifle used in Florida. He is calling on Coffman to cut his long-standing ties to the National Rifle Association.

A mile from Coffman’s district is Columbine High School, where two teenagers killed 13 people and then themselves in 1999.

Questioners on Tuesday repeatedly brought up the NRA’s giving to Coffman’s campaigns, which totals more than $30,000 since he first ran in 2008.

One woman spoke of her 5-year-old granddaughter: “The idea of her going to a public school and having to go through drill after drill after drill to protect her from an assault weapon coming into her school sickens me beyond belief. ... I ask you, stop taking money from the NRA.”

Another woman pressed him on the recent concealed-carry vote: “Can you explain to your constituents why you sided with the NRA instead of our children’s lives?”

Said Coffman, “They support me based on what I do, and I don’t support them based on what they do. And I’m for responsible gun ownership.”

Whether the gun debate will remain at the center of the campaign for Coffman’s seat is a matter of considerable doubt.

The issue is far from a centerpiece for the incumbent. Asked during a session with reporters what he would say to voters who liked his own views on combating gun violence or revamping immigration but were frustrated with the GOP’s ability to take any action, Coffman talked about the tax bill instead before conceding some frustration.