Appalachia is supposed to be a one of Barack Obama’s biggest weak spots. But judging from a surprise work stoppage at the Blacksville No. 2 coal mine in West Virginia, Mr. Obama evidently has some pockets of support there.

Last Monday more than 440 members of the United Mine Workers of America took the day off, halting production at the Blacksville mine. The union declared it a Memorial Day, largely to protest what union officials said was an anti-Obama ad that the National Rifle Association was filming at the mine.

Phil Smith, the union’s communications director, said that the mine’s owner, Consol Energy, allowed the film crew to go on the property, and that the crew asked several miners: “How do you feel about having your Second Amendment rights taken away if Obama becomes president.”

Word spread to several miners who supported Senator Obama, someone called union headquarters in Virginia, and soon Cecil Roberts, the president of the parent union, declared a Memorial Day (which is allowed under the contract) to protest the NRA’s filming (and to show support for Mr. Obama).

“This was a surprise visit,” said Eric Greathouse, safety chairman of UMWA Local 1702, in an interview on WBOY, a television station in Clarksburg W.Va. “A lot of the miners felt that this was a direct slap in the face of the union because they were trying to coerce our people into saying things against Barack Obama.”

The parent union has endorsed Mr. Obama, asserting that he would be better than Senator John McCain for the nation’s workers and labor unions.

Andrew Arulanandam, the N.R.A.’s director of public affairs, said that the film crew had been welcomed to the site. They interviewed a few people and left without incident.

“Union members are the backbone of the N.R.A.’s membership,” Mr. Arulanandam said. He said the protest “is clearly mischief driven by the Obama campaign.”

Thomas F. Hoffman, Consol’s senior vice president for external affairs, said the company meant no harm by letting the N.R.A. crew film at the mine. He said that an N.R.A. film crew had interviewed some miners at Blacksville No. 2 several years ago without any problems.

But the company, based in Canonsburg, Pa., was surprised by the work stoppage. “We were disappointed that the whole thing came out the way it came out,” Mr. Hoffman said.

Mr. Hoffman said that Consol asked the N.R.A. not to use any of the interviews done at Blacksville in any future ads, and he said the N.R.A. had agreed. He said the union went ahead with its work stoppage even though it had been informed that the interviews would not be used.

Mr. Smith, the union spokesman, said the work stoppage was justified. “Our members were a little concerned about being led down a garden path,” he said. “We were upset that the company allowed the N.R.A. to come on its property and try to use our members for political purposes knowing we had already endorsed Obama and a lot of our members had already endorsed Obama.”