The Senate's package of gun control legislation prompted by the mass murder of 20 children at Sandy Hook Elementary School may or may not be dead, but the relationship between the National Rifle Association and former A-rated advocate Sen. Joe Manchin (D-W.V.) sure seems like it's on life support.

Sandy Hook, Manchin said in December, made him rethink his opposition to gun-safety legislation, and he pledged to sit down with his "friends at the NRA" and work out "a sensible, reasonable approach" to curbing gun violence. The NRA did indeed work with Manchin and Sen. Pat Toomey (R-Pa.) to draft a bill strengthening federal background checks on gun buyers.

Things went downhill from there. The NRA became a driving force behind sinking the Manchin-Toomey legislation, along with the broader package of gun-control measures. Then, last week, the NRA started running ads against Manchin in West Virginia, promising to spend $100,000 to run the attack ad in heavy rotation. "Manchin is working with President Obama and New York Mayor Michael Bloomberg," the ad says. "Concerned? You should be. Tell Sen. Manchin to honor his commitment to the Second Amendment and reject the Obama-Bloomberg gun control agenda."

Manchin isn't up for re-election until 2018, but on Thursday morning, he struck back, debuting his own ad suggesting that he's more in line with gun owners than "the NRA's Washington leadership." (Watch the ad above) "They just don't want to get involved," he said on MSNBC's Morning Joe, which showcased the ad. "They want this paranoia going on, and I'm not going to stand back and let them." He said he's also spending $100,000 on his ad buy.

Here's Politico's Mike Allen and the Morning Joe crew with some background on the NRA's feud with Manchin:

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