The memo, obtained first by The Hill, outlines reasons why Democrats believe Jenkins's campaign launch has "made a thud."

They include the fact that Jenkins may face a primary, that he previously contributed to Rahall and the fact that he wasn't the National Republican Congressional Committee's first choice to run for the seat.

Jenkins switched parties to challenge Rahall, losing his leadership positions in the state senate as a result.

In its memo, the DCCC characterized the switch as Jenkins "abandon[ing] his alleged principles in favor of his own spineless self-interest."

He'll likely have some trouble drawing a distinction between himself and Rahall. The DCCC notes that Jenkins contributed to the congressman in 2010, after the health care reform law passed. Rahall, too, contributed to Jenkins's campaign.

And he may indeed face a primary challenge in former state Rep. Rick Snuffer, who has twice before challenged and failed to defeat Rahall, but, as the DCCC notes in its memo, indicated he could run again for the nomination.

The DCCC also notes that Jenkins wasn't Republicans' first choice, as their top recruit, state Sen. Bill Cole, opted out of the race.

The memo, however, belies the fact that Rahall is vulnerable heading into reelection. He's won reelection with solid margins every time and has beaten a party-switching candidate before. But his eight-point lead last cycle was the slimmest he's seen in decades, and Republicans are still hoping that the increasingly red tint of the state will help them oust the incumbent.

National Republican Congressional Committee spokesman Daniel Scarpinato said that the DCCC memo was evidence of "panic" over Rahall's chances at reelection.

“National Democrats are trying desperately to mask their panic. Both Republicans and Democrats in southern West Virginia are uniting around Evan Jenkins because they are fed up with the Obama’s War on Coal. Sen. Cole is proudly stumping for Evan as his campaign chairman. The contrast between Rahall and Jenkins is simple: Rahall voted for and supports Obama; Jenkins does not,” Scarpinato said. 

This piece was updated at 11:20 a.m. to reflect comment from the NRCC.