The White House is working with its allies on a well-financed campaign in Washington and around the country to shift public opinion toward stricter gun laws and provide political cover to lawmakers who end up voting for an assault-weapons ban or other restrictions on firearms.

With President Obama preparing to push a legislative agenda aimed at curbing the nation’s gun violence, pillars of his political network, along with independent groups, are raising millions of dollars and mapping out strategies in an attempt to shepherd new regulations through Congress.

But the efforts, designed in large part to counter opposition from the National Rifle Association, face serious political obstacles on Capitol Hill. The NRA spent more than $20 million on federal election campaigns last year, and its lobbying muscle extends from Washington to state capitals around the country.

Most Republicans in the GOP-controlled House also oppose additional gun regulations, as do some key Democrats in the Senate — meaning that the groups aligned with Obama will have to persuade dozens of skeptical lawmakers to vote for the president’s eventual proposals.

The groups, whose leaders are in regular contact with the White House, are working to enlist religious leaders, mayors, police chiefs and other influential constituents to lobby their local lawmakers in their home districts. The organizations also plan to stage rallies at congressional town hall meetings across the country in much the same way tea party activists mounted opposition in 2009 to Obama’s health-care overhaul.

Majority sees Connecticut shooting as societal problem

A trial run for the burgeoning campaign came this week when the Coalition to Stop Gun Violence ran hard-hitting ads in North Dakota and Capitol Hill newspapers against Sen. Heidi Heitkamp (D-N.D.), who said Sunday that some of the gun measures Obama is considering are “extreme.” After the ads — which told Heitkamp “Shame on you” — the freshman senator’s office issued a statement opening the door to supporting some gun-control measures.

“You have to get those members of Congress who think the easiest position is to be with the NRA to think that someone will walk up to them in the supermarket and say, ‘Why can’t we just have background checks?’ ” said Neera Tanden, president of the Center for American Progress, a liberal think tank helping to coordinate the effort. “They have to think of these as mainstream issues.”

Other organizations active in the effort include liberal interest groups, labor unions and Mayors Against Illegal Guns, which is led and financed by New York Mayor Michael R. Bloomberg (I).

A political action committee, Americans for Responsible Solutions, was launched this week by former congresswoman Gabrielle Giffords and has picked up seven-figure donations from major Democratic benefactors.

Laurene Powell Jobs, the widow of Apple founder Steve Jobs, and Ron Conway, a leading Silicon Valley angel investor, are helping finance the Giffords group and will co-host a fundraiser in San Francisco this week, an organizer said. Two wealthy Texas lawyers, Steve and Amber Mostyn, told news outlets Wednesday that they had given $1 million to the organization. Giffords was shot in the head two years ago in a mass shooting outside a supermarket in Tucson.

“The real challenge that these organizations will have is how much money will they be able to raise in order to effectively communicate their side of the story,” said Ron Bonjean, a Republican strategist and former top congressional aide. “Those who are in favor of keeping the status quo have massive resources that can do the same thing.”

While groups such as the Brady Campaign to Prevent Gun Violence have long lobbied for stricter gun laws, last month’s massacre at an elementary school in Newtown, Conn., has spurred many progressive organizations, millionaire donors and other activists to begin focusing on the issue.

White House working group

An administration working group led by Vice President Biden is preparing a set of gun-control proposals that could be announced by the end of this month, perhaps as part of Obama’s State of the Union address. Lawmakers say Congress could begin considering gun bills in two weeks.

Biden, after a meeting Wednesday with victims of gun violence and leaders of gun-safety organizations, vowed that the administration will take swift action.

“This is a problem that requires immediate attention,” Biden said. “I want to make clear that we’re not going to get caught up in the notion that, unless we can do everything, we’re going to do nothing.”

The White House is considering a wide range of legislative proposals, including a ban on assault weapons and high-capacity ammunition magazines, as well as universal background checks on gun buyers. Biden also said Wednesday that Obama may take executive actions that sidestep Congress, although he did not provide details.

Biden’s comments sparked an immediate and sharp backlash from Republicans. “The Founding Fathers never envisioned Executive Orders being used to restrict our Constitutional rights,” Rep. Jeff Duncan (S.C.) said in a statement. “We live in a republic, not a dictatorship.”

Biden’s meetings with interest groups to build consensus will continue Thursday, when he will meet with representatives of the NRA and other gun-owner groups as well as a representative from Wal-Mart, one of the nation’s leading gun retailers. The NRA, which has signaled its opposition to any new gun regulations, has suggested placing armed guards at all of the nation’s schools in reaction to the Connecticut shootings.

‘Gun-violence prevention’

Earlier this week, senior White House aides organized a conference call with a roster of private foundations, some of which are funding polls, public ed­ucation campaigns and other anti-gun-violence­ initiatives.

One of the groups was the Chicago-based Joyce Foundation, a major funder of gun-control programs that counted Obama as a board member from 1994 to 2002. Nina Vinik, director of the foundation’s anti-gun-violence initiative, said research suggests that the public is poorly informed about current gun laws.

“Most people assume that our gun laws are in fact much more expansive and stronger than in fact they are,” Vinik said.

Some of the groups plan to use television and newspaper advertisements to paint laws restricting guns as a mainstream, common-sense idea. Some advocates have also stopped calling their efforts “gun control,” preferring “gun-violence prevention” instead.

One objective is to drive a wedge between the NRA’s policy agenda and the views of a majority of its members, activists said. Mayors Against Illegal Guns commissioned a study last year by Republican pollster Frank Luntz that found that 74 percent of NRA members support requiring criminal background checks for anyone purchasing a gun.

“This isn’t a battle about going dollar for dollar with the NRA,” said Winnie Stachelberg, executive vice president at the Center for American Progress. “It’s about drawing attention to the fact that the NRA officials and lobbyists and the NRA membership are in completely different places. Exposing that gap is a critical component of that effort.”

Sari Horwitz and David Nakamura contributed to this report.