An effort to paint Democratic Senate hopeful Chris Van Hollen as soft on gun control has drawn the attention of the White House, which criticized as misleading a super-PAC ad attacking the Maryland congressman.

The unusual intervention, which caused the PAC to remove President Obama’s image from the ad, illustrates a central tension between Van Hollen and rival Rep. Donna F. Edwards, D-Maryland, in the hotly contested primary for a rare open Senate seat.

While Van Hollen has touted his experience drafting major legislation, Edwards has poked holes in that record as insufficiently progressive.

This particular dispute is over whether, in an effort to win support from Republicans and conservative Democrats, Van Hollen was right to exempt the National Rifle Association from 2010 legislation aimed at making shadowy political groups disclose their donors. Senior Democrats, including President Obama, were in favor of exempting the NRA – and the liberal Sierra Club – in hopes of generating enough support in Congress for the legislation to pass.

Edwards opposed that deal and has used it as a key element of her depiction of Van Hollen as prone to engage in backroom shenanigans. Van Hollen has called her attacks dishonest and her stance an example of an uncompromising, ineffective approach to politics.

With less than two weeks until the April 26 primary, polls show the race is very close. An NBC-Marist poll released Tuesday gave Van Hollen a six-point edge; Edwards led by four points in a Washington Post-University of Maryland survey released last week. Each result is within its survey’s margin of error.

The battle is being stoked on both sides by the same obscure groups Van Hollen hoped to target with the donor-disclosure legislation.

The Working for Us PAC, a group that has been backed by labor unions in the past but has yet to disclose its donors this cycle, aired the ad that raised the White House’s ire. It featured a clip of an emotional Obama discussing gun control and the 2012 massacre of schoolchildren in Newtown, Connecticut. Afterward, a narrator says: “Chris Van Hollen met with NRA lobbyists to craft a loophole that would let the NRA skirt a new campaignfinance law and block gun control.”

A top adviser to the president reached out to Working for Us to say that “the use of the president’s image and statement in this context were misleading,” a White House spokesman said. The intervention was first reported by Politico.

Rep. Steny H. Hoyer, D-Maryland, also called the ad “dishonest,” adding that Van Hollen’s bill “had nothing to do with gun violence.”

Working for Us said it would remove Obama from the ad but stood by its message. The ad “speaks to how Donna Edwards isn’t a typical D.C. insider who compromises her values just to make a deal,” spokesman Joshua Henne said.

Edwards has levied similar attacks on Van Hollen in debates, and released her own ad on the subject Wednesday.

That ad, playing in Baltimore, focuses on a 3-year-old girl killed by a stray bullet in the city two years ago and features Edwards touting the defeat of the donor-disclosure legislation.

The bill passed the House despite defections from about three dozen House Democrats, many of whom – including Edwards – opposed the decision to leave out the NRA. But it failed in the Senate, where despite the NRA exemption, it did not win any Republican support.

Craig Holman, a lobbyist for the good-governance group Public Citizen, which pushed for Van Hollen’s legislation, said he “wasn’t comfortable” with the NRA exemption, “but I didn’t really think it would do much damage either.”

He noted that groups such as the NRA were not the main target of the legislation, because their goals are well known. Instead, the bill was an effort to get more information from super PACs and other groups whose agendas are less clear.

Van Hollen says that thecampaign-finance disagreement has nothing to do with his record on gun control.

Both he and Edwards have F ratings from the NRA. Van Hollen has been a strong voice for gun restrictions on Capitol Hill and as a state lawmaker helped push through legislation requiring trigger locks on guns. “I have led the fight against the NRA,” he said angrily at a forum in Silver Spring on Monday evening. “People should not be misled on the issue.”

The congressman said Edwards’s decision to oppose the donor-disclosure legislation was emblematic of an uncompromising attitude that, he said, leads her to be ineffective.

A pro-Van Hollen super PAC backed by the Service Employees International Union is echoing that criticism. “We need a senator who does more than talk,” says the narrator in an attack ad the group aired this week. “It was Chris Van Hollen who took on the NRA to pass tougher gun laws.”

Like Working for Us, the pro-Van Hollen group has not disclosed its donors. Created just for this race, it operates under the name Committee for Maryland’s Progress.

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