Congressman Nick Rahall (D-W.Va.) chats backstage with drummer Bill Kreutzmann before the Grateful Dead's concert at the Verizon Center. (Photo courtesy of Rep. Nick Rahall's office)

Longtime Rep. Nick Rahall (D-W.Va.) trails in his reelection campaign by double digits, according to a new Republican poll.

State Sen. Evan Jenkins (R) leads Rahall 54 percent to 40 percent in the survey, which was conducted by the Tarrance Group for the National Republican Congressional Committee and Jenkins's campaign. The poll was shared with the Washington Post.

The finding comes on the heels of an ad blitz from a number of conservative groups keen on taking the seat in the heavily conservative district, which Rahall has held down for nearly four decades.

The conservative groups, led by the Chamber of Commerce, the Koch brothers-backed Americans for Prosperity and the American Energy Alliance, have spent about $1.4 million since late 2013 -- the vast majority of it attacking Rahall.

Democratic spending on Rahall, meanwhile, has lagged far behind, with the super PAC House Majority PAC spending about $160,000.

Any poll from a partisan pollster should be viewed with a degree of skepticism, but the new survey harkens back to polling done in 2010 that showed longtime Democratic incumbents in conservative districts facing very difficult races for the first times in their careers.

While the GOP toppled many of those incumbents -- largely in 2010 but also some in 2012 -- Rahall has so far escaped top-tier challenges. He defeated state Sen. Rick Snuffer (R) by 8 points in 2012.

But the new poll suggests the heavy ad spending -- $1.4 million goes a long way in West Virginia -- has taken a toll. Rahall's approval rating is just 38 percent, with 54 percent rating him negatively. Rahall is viewed favorably on a personal basis by 44 percent of the district's voters, while 49 percent view him unfavorably.

Jenkins is less well-known, but his favorable rating is more than three times his unfavorable rating.

It's not clear whether Democratic polls are bearing out similar results, but Rahall was added to the Democratic Congressional Campaign Committee's incumbent-protection program, known as "Frontline," on Friday of last week.

Rahall's district went for GOP presidential nominee Mitt Romney 66-32 percent in 2012. Much of the conservative advertising in the district has tied Rahall to Obamacare and what the groups call President Obama's "war on coal. Coal is a major industry and issue in West Virginia.

Rahall's is the second most conservative district held by a Democrat. The holder of the most conservative district, Rep. Jim Matheson (D-Utah), is retiring this year.

The poll surveyed 405 likely voters by telephone -- 30 percent of them via cell phone -- between March 3 and March 5. It has a margin of error of plus or minus 4.9 percent.

Update 9:58 a.m.: House Majority PAC is now up with a new $65,000 ad buy on Rahall's behalf.