U.S. Sens. Susan Collins and Angus King are downplaying the significance of an advertisement by the National Rifle Association that urges Maine voters to convince their senators to reject President Barack Obama’s gun control agenda.

“I haven’t seen it,” King said Thursday, referring to a full-page ad in Thursday’s Bangor Daily News. “This story isn’t going away. I’m working on the issue. I’ve sat down with gun owners and sportsmen in Maine. I’ve sat down with gun-control advocates in Maine. I’m trying to come up with what I think are the most effective proposals that will actually diminish gun violence while at the same time protect Second Amendment rights.”

Collins said she had not seen the ad, which mentions the senators by name. Like King, she said she has met with people on all sides of the gun debate, which was renewed by the mass shootings at an elementary school in Connecticut in December.

“I do believe that the common thread in all these horrific mass shootings is mental illness, and I was surprised that the president did not even talk about that in his State of the Union address” on Feb. 12, Collins said.

Republicans, prodded by the NRA, say they are focused on improving the mental health system and enforcing laws already on the books instead of creating new laws.

Obama has called for universal background checks and a ban on some guns and high-capacity magazines, measures that the NRA opposes.

The NRA ad, which ran in daily newspapers in five states, is headlined, “Will Obama’s gun control proposals actually work?” The next line reads, “His own experts say ‘No.'”

The ad features a memo from the National Institute of Justice to the president that appears to say that his proposals would not work without universal registration or confiscation of some guns. It ends with a call for citizens to call their senators and “tell them to oppose Obama’s gun control proposals and to fix our broken mental health system.”

University of Maine political science professor Mark Brewer said the featured memo is meaningless, given that the president gets thousands of memos each week on a variety of viewpoints, and no one memo informs the president’s policies.

“But that doesn’t mean that the average person knows this,” Brewer said. “They could think ‘Obama’s own people are telling him not to do this.'”

Jacqueline Otto, an NRA spokeswoman, said the powerful lobbying group placed ads in newspapers in Arkansas, Louisiana, Maine, North Carolina and West Virginia.

Four of those states have Democratic senators who are up for re-election in 2014. In Maine, Collins, a moderate Republican, is up for re-election.

Asked whether Collins was targeted because of her less-than-enthusiastic support for the NRA, Otto said the ad is simply meant to “educate and inform voters in Maine.”

Brewer, however, said the NRA could be sending Collins a message.

“There is no way she is vulnerable in the general election,” he said of Collins, a three-term senator, “but this might be an opportunity for the NRA to shore up the support of someone they are not 100 percent sure of.”

Collins recently received a C+ rating from the NRA, which is “horrible for a Republican,” Brewer said.

She split from her party in 2004 when she voted to extend the federal ban on assault weapons.

Collins received nearly $20,000 in campaign donations from the NRA’s political action committee from 1996 to 2002, but she has not received any contributions since then.

She also received more than $17,000 in contributions from Richard Dyke, former owner of Bushmaster Firearms Inc. in Windham, but none since 2007.

On Thursday, Collins said she has co-sponsored a bipartisan bill that would improve mental health care by raising quality standards and expanding access. However, it’s not clear how that effort would be funded, at a time when budget cuts are dominating much of the discussion in Washington, particularly within her own party.

Collins also has co-sponsored a bill to crack down on “straw buyers,” people who buy guns for others, including criminals who would not pass background checks.

King, who is independent but caucuses with Senate Democrats, said he has not introduced any legislation or co-sponsored any gun-related bills. He said the NRA has a legitimate point, but it’s not the only point.

“They represent four million members and there are something like a hundred million gun owners, so clearly they don’t speak for all gun owners,” he said.

Otto said she did not know whether the NRA was prepared to buy additional space in Maine newspapers.

Brewer said the NRA probably advertised in the Bangor newspaper because it covers a rural, more conservative area.

The paper drew criticism last week because it submitted Freedom of Access Act requests for records of all concealed-weapon permit holders in Maine.

The request was rescinded after a backlash from lawmakers and threats from advertisers and readers. On Tuesday, the Legislature passed emergency legislation to halt the release of any information on concealed-weapon permits for 60 days.

“I guarantee the NRA ad person who bought that ad got a chuckle about putting it in a newspaper that tried to get information about permit holders and then had to back down from that request,” Brewer said.