LAREDO, Tex. — In this gun-friendly border city, where Tuesdays are “ladies’ nights” at the shooting range and pistols in hip holsters are a common sight, Representative Henry Cuellar is a proud defender of the Second Amendment, the lone House Democrat from Texas with an “A” rating from the National Rifle Association.
“This is not New York, this is Texas,” Mr. Cuellar said in an interview. “So you talk about guns, you talk about God, you talk about trucks.”
But times are beginning to change here in Texas, where a string of mass shootings in August left 29 people dead, and in Washington, where gun safety is now front and center on the congressional agenda.
Mr. Cuellar is emblematic of the shift. He voted this year for a House bill expanding background checks for gun buyers, which will almost certainly cost him his N.R.A. “A” rating and the campaign contributions and endorsement that went along with it.
On Monday, with Congress back from its August recess, a bipartisan group of mayors and police chiefs met with top White House advisers to push for action on gun safety, and later joined top Democrats on Capitol Hill in demanding passage of the background checks bill in the Senate, where it is currently blocked.
Mr. Cuellar’s quiet evolution, though he does not call it that, tells a larger tale of how the Democrats have abandoned the N.R.A. — and also hints of unrest among Republicans, especially those who have had mass shootings in their districts or home states.
Representative Michael R. Turner, Republican of Ohio, is from a district that includes Dayton, where a gunman killed nine people outside a bar last month. He now backs a ban on the sale of military-style weapons. So does Representative Brian Mast, Republican of Florida, where a 2018 mass shooting at Marjory Stoneman Douglas High School in Parkland galvanized a youth movement for gun safety.
Mr. Cuellar, whose district includes Sutherland Springs, where a gunman with an AR-15-style rifle killed 26 people at a Baptist church in 2017, does not support an assault weapon ban. But his vote in favor of expanding background checks — an idea that President Trump has embraced and that is likely to be considered in the Senate — buoyed gun safety advocates.
“Change is rippling across America, and he’s part of that change,” said John Feinblatt, the president of Everytown for Gun Safety, an advocacy group. “He is part of an evolving Democratic Party on this issue, and I also believe that the Republican Party is behind them and beginning to evolve, too.”
For Mr. Cuellar, evolution on guns may be necessary for political survival. In the last election cycle, he was one of only three House Democrats — the others are Representatives Sanford D. Bishop Jr. of Georgia and Collin C. Peterson of Minnesota, who also have A ratings — who took contributions from the N.R.A.’s political action committee.
Now, he is facing a new reality: a primary challenge from the left.
His opponent, Jessica Cisneros, 26, an immigration rights lawyer who once worked as Mr. Cuellar’s intern, is backed by the Justice Democrats, the group that helped elect Representative Alexandria Ocasio-Cortez, the liberal firebrand from New York. Ms. Cisneros has demanded that Mr. Cuellar give back his N.R.A. contributions, including $6,950 he received for his 2018 race.
In 2017, another House Democrat, Representative Tim Ryan, who also once had an A rating from the N.R.A., announced he would donate roughly $20,000 that the gun lobby gave him to gun safety groups.
“I truly believe that somebody like him, somebody that takes money from the N.R.A., somebody that received support and an A rating from the N.R.A., cannot call themselves a Democrat,” said Ms. Cisneros of Mr. Cuellar. “I think it’s very tone-deaf.”
On Monday, Senator Elizabeth Warren, Democrat of Massachusetts, a 2020 presidential candidate who has built her campaign around progressive activism, endorsed Ms. Cisneros, saying that people in the district “deserve a Democrat that will be on the side of working people, not the side of big money and obstructionist Republicans.”
Mr. Cuellar said he had no intention of returning the N.R.A. money, which he characterized as minimal and without influence on his votes. He called Ms. Cisneros and her backers “justice socialists” and said that in a district like his, which includes “urban areas, rural areas, people that might not believe in guns, people that do believe in guns,” he has “balancing work” to do.
“I am for reasonable gun reform,” he said during the interview, in a busy taco restaurant. “But I’m not going to take guns away from people like they want to do.”
Texas has some of the most permissive gun laws in the nation. A law that took effect Sept. 1, for example, greatly expanded where licensed gun owners may carry their firearms, including churches. But the recent shootings have ratcheted up pressure on Republicans. On Friday, Lt. Gov. Dan Patrick, a staunch conservative, said he would defy the N.R.A. to push for background checks on private gun sales.
In Laredo, Mr. Cuellar’s race may reveal whether there is still a home in the party for a Democrat who talks about gun rights. His district stretches from San Antonio down a rural highway lined by hunting ranches to Laredo, where a local gun store, the Arena Gun Club, offers free rentals of fully automatic weapons each week on “Machine Gun Monday.” Last week, it was doing a brisk business at its indoor shooting range.
Daniel Cruz, 28, a truck driver who had just hit 14 bull’s-eyes on each of 14 targets, echoed the philosophy of many Texans when he said the answer to mass shootings was not fewer guns but more. He lamented that not enough people take advantage of Texas’ open-carry laws.
“These shootings are in public places,” he said, “but nobody has a gun to fire back.”
But in a working-class neighborhood across town, about two dozen enthusiastic, mostly millennial volunteers gathered in the backyard of one of Ms. Cisneros’s supporters. The recent massacres in El Paso, Midland and Odessa were very much on their minds.
The El Paso shooting, in a border city like Laredo, struck a particular nerve. A white gunman with an AK-47-style rifle drove 10 hours to a Walmart, where he shot and killed 22 people, targeting Latinos.
“I feel like Laredo is a mini-version of El Paso,” said Eddie Gomez, 26, one of the volunteers. “It felt very deliberate, it felt very personal. It felt like an attack on what we are, on my people.”
Mr. Cuellar, 63, a lawyer and former state legislator first elected to the House in 2004, won in 2018 with 84 percent of the vote, and Republicans did not bother to field a candidate against him. He prides himself on bipartisanship. He once served as secretary of state to a Republican governor, Rick Perry, and endorsed another Republican, George W. Bush, for president in 2000.
Like many Texans, he grew up around firearms. The eldest of eight children, Mr. Cuellar lived on what he called “a ranch in the hill country” managed by his father, who kept guns for hunting and protection.
“My dad was the best shot,” Mr. Cuellar said. “He could see a deer 100 yards away.”
After the church massacre in Sutherland Springs, most Democrats were clamoring for expanded background checks and an assault weapons ban. Mr. Cuellar was not among them.
Instead, in light of news that the gunman had obtained his weapon despite a domestic violence conviction, Mr. Cuellar joined Republicans, who then led the House, to push the so-called Fix N.I.C.S. bill. That bill made modest improvements to the National Instant Background Check System.
The measure was paired in the House with one that relaxed restrictions on the carrying of concealed weapons across state lines. Mr. Cuellar was one of only six Democrats who voted in favor.
In a nod to gun enthusiasts, he also invited the so-called hero of Sutherland Springs, Stephen Willeford, who grabbed his own military-style weapon and chased down the gunman, to Mr. Trump’s State of the Union address.
“Henry is different than most Democrats, and I can appreciate that,” Mr. Willeford said in an interview. “He bucks the system of his own party — but not all the time.” Mr. Willeford added that he strongly opposed the House background check bill that Mr. Cuellar voted for this year.
That House bill, adopted in February, would extend background checks to all private gun sales, including those at gun shows and over the internet. The congressman said his shift reflected his pragmatism. There was no point in calling for background checks when Republicans ran the House, he said, but with Democrats in the majority, “we’re pushing” for it.
“What he’s trying to do is an interesting cultural straddling,” said Kris Brown, the president of Brady, the gun safety group. “He’s not going to have an A rating anymore, and look, I give him credit for that. I just think that ultimately, in order to get the lifesaving measures that we need enacted, we need more politicians to lead on this issue.”
The N.R.A., through a spokeswoman, declined to comment on Mr. Cuellar. So far, the organization has contributed to only one House Democrat for the 2020 election cycle: Mr. Peterson of Minnesota. It has not released its ratings for 2020. While Mr. Cuellar said the gun lobby’s endorsement had been helpful to him, he shrugged when asked if he worried about losing it.
“It doesn’t matter,” he said. “What’s important is that I support the Second Amendment.”