The political momentum in the gun control debate has shifted in the year leading up to this weekend’s mass shootings in El Paso, Texas, and Dayton, Ohio, with gun control advocates taking a more empowered stance and the National Rifle Association consumed by internal power struggles.

The major gun control organisations, propelled by funding from supporters like Michael R Bloomberg, the former New York City mayor, and grassroots networks across the country, have enacted new laws — mostly in Democratic-controlled states — and, for the first time in 25 years, passed a significant gun control bill in the House.

But the gun lobby’s structural advantages, built over decades and defended by Donald Trump, the US president, and congressional Republicans, remain in place: an NRA budget that dwarfs what even Mr Bloomberg has spent, a Republican Senate majority disinclined to consider gun-control legislation, and a base of primary voters for whom the NRA’s endorsement is a critical seal of approval.

The net effect is a playing field on gun issues that is far more level than it has been since NRA-backed Republicans took over Congress in 1994, sparking one of the country’s most bitter, partisan culture wars.

Yet in the immediate aftermath of the weekend massacres, there were few signs the El Paso and Dayton mass shootings would lead to calls for additional gun restrictions any different from those already being pushed by Democrats.

El Paso mass shooting: 20 killed at Walmart store Show all 39 1 /39 El Paso mass shooting: 20 killed at Walmart store El Paso mass shooting: 20 killed at Walmart store CCTV images of the gunman identified as Patrick Crusius The 21 year old, as he entered the Cielo Vista Walmart store in El Paso. The gunman was armed with an assault rifle and opened fire on shoppers at a packed Walmart store, killing 20. KTSM 9/AFP/Getty El Paso mass shooting: 20 killed at Walmart store Law enforcement agencies respond The Texas city’s police chief said the assault on a Walmart store on Saturday, which left another 26 people wounded, was being investigated as a potential hate crime. AFP/Getty El Paso mass shooting: 20 killed at Walmart store Shoppers exit with their hands up Shoppers exit with their hands up after a mass shooting at a Walmart in El Paso, Texas, U.S. August 3, 2019. REUTERS/Jorge Salgado NO RESALES. NO ARCHIVES. STRINGER Reuters El Paso mass shooting: 20 killed at Walmart store FBI released a picture of gunman Patrick Crusius The police officially identified the 21-year-old white male from Allen, Texas, a Dallas suburb some 650 miles east of El Paso. FBI/AP El Paso mass shooting: 20 killed at Walmart store A woman reacts after the mass shooting The attack came just minutes after a far-right manifesto appeared online. If authentic, it would make it the third mass shooting this year announced in advance on the website, which often features far-right and racist content. Reuters El Paso mass shooting: 20 killed at Walmart store Law enforcement responds to the active shooter The racist four-page document, titled “The Inconvenient Truth”, calls the Walmart attack “a response to the Hispanic invasion of Texas” and expresses support for the gunman who killed 51 people at two mosques in Christchurch, New Zealand earlier this year. AFP/Getty El Paso mass shooting: 20 killed at Walmart store A shopper hiding with an old lady behind the return and exchanges counter as the shooting began. Aaron Castaneda/Reuters El Paso mass shooting: 20 killed at Walmart store Ambulances in the car park near the scene It is ranked as the eighth-deadliest mass shooting in modern US history, after a 1984 shooting in San Ysidro, California, that claimed 21 lives. AP El Paso mass shooting: 20 killed at Walmart store Kendall Long (left) comforts Kianna Long (right) who was in the freezer section of Walmart. EPA El Paso mass shooting: 20 killed at Walmart store epa07755367 Police stand at attention after a shooting at a Walmart in El Paso, Texas, USA, 03 August 2019. According to reports, at least one person was killed and at least 18 people injured and transported to local hospitals. One suspect is in custody. EPA/IVAN PIERRE AGUIRRE IVAN PIERRE AGUIRRE EPA El Paso mass shooting: 20 killed at Walmart store Shoppers exit with their hands up. Reuters El Paso mass shooting: 20 killed at Walmart store Shopping carts sit next to a curb after the shooting. EPA El Paso mass shooting: 20 killed at Walmart store El Paso Fire Medical personnel arrive at the scene. AP El Paso mass shooting: 20 killed at Walmart store Walmart employees react after. AP El Paso mass shooting: 20 killed at Walmart store A woman runs to police near the scene. AP El Paso mass shooting: 20 killed at Walmart store Several law enforcement agencies respond. AP El Paso mass shooting: 20 killed at Walmart store People arrive at MacArthur Elementary looking for family and friends as the school is being used a re-unification centre. AP El Paso mass shooting: 20 killed at Walmart store Residents Erica Rios, 36, and Alma Rios, 61, cry outside a reunification centre. AFP/Getty El Paso mass shooting: 20 killed at Walmart store People gather in Juarez, Mexico, in a vigil for the Mexican nationals who were killed. AP El Paso mass shooting: 20 killed at Walmart store A child takes part in a vigil in Ciudad Juarez AFP/Getty El Paso mass shooting: 20 killed at Walmart store Francisco Castaneda joins mourners taking part in a vigil at El Paso High School. Reuters El Paso mass shooting: 20 killed at Walmart store Presidential candidate and former congressman Beto O'Rourke, right, meets with mass shooting survivor, Rosemary, at University Medical Centre Beto O'Rourke Facebook via AP El Paso mass shooting: 20 killed at Walmart store From left, Melody Stout, Hannah Payan, Aaliyah Alba, Sherie Gramlich and Laura Barrios comfort each other during a vigil for victims of the shooting. AP El Paso mass shooting: 20 killed at Walmart store A sign is posted near the scene Getty Images El Paso mass shooting: 20 killed at Walmart store Police cars parked below the Walmart sign block a road outside while investigating. EPA El Paso mass shooting: 20 killed at Walmart store Sherie Gramlich reacts during a vigil. AP El Paso mass shooting: 20 killed at Walmart store A man places flowers at the site Reuters El Paso mass shooting: 20 killed at Walmart store People take part in a rally against hate a day after a mass shooting at the Walmart store Reuters El Paso mass shooting: 20 killed at Walmart store Lupe Lopez holds a picture of a victim during a vigil for victims AP El Paso mass shooting: 20 killed at Walmart store People take part in a rally against hate a day after a mass shooting at a Walmart store, in El Paso, Texas, U.S. August 4, 2019. REUTERS/Jose Luis Gonzalez JOSE LUIS GONZALEZ REUTERS El Paso mass shooting: 20 killed at Walmart store Elsa Mendoza Marquez, a Mexican schoolteacher who was married and the mother of two adult children, was one of the victims Getty El Paso mass shooting: 20 killed at Walmart store People with the Mexican flag and the US flag take part in a rally against hate a day Reuters El Paso mass shooting: 20 killed at Walmart store People raise their arms in the air during a vigil for victims AP El Paso mass shooting: 20 killed at Walmart store People react and embrace each other Getty El Paso mass shooting: 20 killed at Walmart store Women light candles at a make shift memorial at the site of a mass shooting EPA El Paso mass shooting: 20 killed at Walmart store Adria Gonzalez (centre) who is being hailed as a hero for leading some Walmart customers to safety, speaks to the crowd AFP/Getty El Paso mass shooting: 20 killed at Walmart store People hold up their phones AFP/Getty Images El Paso mass shooting: 20 killed at Walmart store Beto O'Rourke speaks to the crowd AFP El Paso mass shooting: 20 killed at Walmart store People react during a prayer and candle vigil organized by the city, after a shooting left 20 people dead at the Cielo Vista Mall WalMart in El Paso, Texas, on August 4, 2019. - A shooting at a Walmart store in Texas left multiple people dead. At least one suspect was taken into custody after the shooting in the border city of El Paso, triggering fear and panic among weekend shoppers as well as widespread condemnation. It was the second fatal shooting in less than a week at a Walmart store in the US and comes after a mass shooting in California last weekend. (Photo by Mark RALSTON / AFP)MARK RALSTON/AFP/Getty Images MARK RALSTON AFP/Getty

Though the US experiences hundreds of mass shootings each year, few have captured enough public attention to force even incremental change. And even in cases when gun control legislation is drafted, the NRA and its allies in elected office have almost always defeated it.

On Sunday, activists and Democrats, including the leading candidates for president, reiterated chronic pleas for the Republican-controlled Senate to take action on the gun control bill that House Democrats passed in February, a measure that would require background checks for all gun buyers.

“The Senate should come back from recess and immediately vote on laws that we know work and save lives,” said Shannon Watts, the founder of Moms Demand Action for Gun Sense in America, the grassroots gun control organisation funded largely by Mr Bloomberg.

“If Congress continues to sit on its hands, then we will work even harder to make sure that we have a gun-sense majority in Congress and a president who will do the right thing.”

“Sickening to learn this morning of another mass murder in Dayton, Ohio overnight,” he tweeted on Sunday. “Two horrifying acts of violence in less than 24 hours. We stand with law enforcement as they continue working to keep Americans safe and bring justice.”

But Senate Democrats may not get off easy by just blaming McConnell. The spate of mass shootings in recent years has led an array of activist groups to adopt positions that were once relegated to the far fringes of the gun debate; these groups now aim to hold accountable Democrats who they believe do not fight hard enough for gun control measures.

“They must do everything in their power, everything in their capacity as a senator, from holding a filibuster, to placing a hold on nominees and key bills, to getting back to DC right now to show the nation that they are willing to act,” said Igor Volsky, the executive director of Guns Down America.

“It’s not enough to simply ask Mitch McConnell to bring something to a vote. They have to use their leverage as a United States senator to shame him into taking action.”

Chris Murphy, the senator for Connecticut who has pushed for gun control legislation since the 2012 elementary school massacre in Newtown, Connecticut, said on Sunday that he had spent the weekend discussing gun control proposals with his Republican colleagues.

If Republicans won’t budge, then Democrats will “have to get together and figure out what leverage we have in the Senate,” Mr Murphy said. But realistically, he said, gun control may only pass the Senate if Democrats control the chamber.

“It’s my responsibility to try to find a legislative path, but I’m not going to take too many kicks at the football if it keeps getting pulled out from under us,” Mr Murphy said. “I think we have had our eyes firmly on the electoral path since the spring of 2013, and we probably have to keep it there.”

Families left heartfelt tributes to the twenty killed when a gunman stormed a Walmart store in El Paso, Texas (AFP/Getty Images) (AFP)

Mike Thompson, Democatic representative for California, who leads the House’s Gun Violence Prevention Task Force, said members were working on additional legislation — including restrictions on high-capacity magazines — despite the challenges of passing the measures in the Senate.

“Sadly, we know that the issue of gun violence prevention is a partisan issue,” Mr Thompson said. “We saw that firsthand with the House Republicans holding up any hearings on gun violence prevention, any votes on gun violence prevention, for 6 1/2 years after Sandy Hook. Once the Democrats took over the House, that changed.

There was no sign over the weekend that Republicans’ opposition to new gun laws had softened. In appearances on Fox News, Kevin McCarthy, representative of California, the House minority leader, and Lt Gov Dan Patrick of Texas blamed violent video games — to which the NRA has long sought to shift blame — for the proliferation of mass shootings.

“We’ve always had guns and evil,” Mr Patrick said in the Fox interview. “I see a video game industry that teaches young people to kill.”

Violent video games are common in many other countries, which do not experience mass shootings at anywhere near the level the US does. But no other country has as many guns: Americans own an estimated 393 million guns, according to a 2018 study, more than the nation’s population.

In a major shift from past presidential campaigns, the 2020 Democratic candidates are unanimous in their support of universal background checks and other restrictions.

Many have gone further, calling for reinstatement of the expired 1994 assault weapons ban — part of a crime bill written by former Vice President Joe Biden — as well as offering more robust proposals. Cory Booker, senator of New Jersey, has called for a federal gun licensing program.

“Enough is enough is enough, and it’s been enough for the past five years,” Mr Biden said at a campaign event in Las Vegas late Saturday.

Both sides have claimed victories at the state level. In 2019, 17 states, all but three of them with Democratic legislatures, and Washington, DC, enacted 35 laws that restricted gun ownership.

At the same time, Republicans in Florida enacted legislation allowing teachers to carry guns in their classrooms, Idaho lowered its age for carrying a weapon without a permit to 18, and several states now allow residents to carry concealed weapons without a permit.

Further complicating the gun-control debate is that the NRA has been in turmoil, mired in financial scandal, investigations, infighting and revelations it was targeted by Russia.

In April, a power struggle with Wayne LaPierre, the NRA’s longtime chief executive, led to the departure of Oliver North, the group’s former president, leading Trump to implore the group to “stop the internal fighting, and get back to GREATNESS – FAST!” But the turmoil continued, and Christopher W Cox, the NRA’s top lobbyist and second-in-command — and a friend of Donald Trump Jr — was forced out in June.

The NRA has turned over thousands of pages of records in congressional investigations of its ties to Russia. It is also facing investigations by the attorneys general of New York and Washington, DC And it is mired in a bitter legal fight with Ackerman McQueen, an advertising firm that was for decades its most influential contractor.

Hundreds turned out in Oregon District to remember the nine people killed in the second US mass shooting in 24 hours on Sunday (Getty Images)

But the NRA remains formidable, with an overall budget that dwarfs that of any gun control group, and it is unlikely to moderate its positions.

After 30 hours of silence following initial reports of the El Paso massacre, the NRA released a statement offering “our deepest sympathies” to victims in El Paso and Dayton.

“We will not participate in the politicizing of these tragedies,” said NRA spokesman Andrew Arulanandam. “As always, we will work in good faith to pursue real solutions that protect us all from people who commit these horrific acts.”

Perhaps a more telling statement came on Saturday morning, before the Texas shooting, when Willes Lee, the group’s second vice president, tweeted: “Where do you feel least safe, most vulnerable? Exactly. A gun free zone. Tell elected officials and business owners they are responsible for innocent people losing lives.”

Still, gun control advocates believe the NRA is in its weakest position since 1994. With Trump in the White House, the organisation can no longer say that a hostile administration is threatening to take away Americans’ guns.

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Some prominent Republicans, including senators Lindsey Graham of South Carolina and Marco Rubio of Florida, do support extreme-risk protection orders, commonly known as red-flag laws. This in itself is a significant shift, and in an interview earlier this year, Mr Rubio said he had been influenced by how routine mass shootings had become.

“I remember being at a confirmation service for my nephew, and somehow the thought crept into my head: What if somebody walked in here now and started shooting?” he said. “I never used to think about those things. So absolutely, it has an impact on people, and people want action.”

After the shooting in El Paso, Mr Graham tweeted that it was “time to do more than pray,” but did not elaborate.

For Democrats in Washington, the political winds on gun control have shifted dramatically since Sandy Hook.

Of the 235 Democrats in the House now, just three received “A” ratings from the NRA last year: reprsentatives Sanford Bishop of Georgia, Collin Peterson of Minnesota and Henry Cuellar of Texas. Mr Cuellar has a Democratic challenger for 2020 who has sought to make his position on gun control an issue in the primary. By contrast, in 2008, voters elected 67 Democrats with A ratings.

Among Democrats, there was little appetite after the El Paso and Dayton massacres for the typical offering of thoughts and prayers for the victims.

“No more thoughts and prayers,” Kamala Harris, senator of California, wrote on Sunday in a fundraising solicitation for three gun control groups. “We need action.”