At the same time the McCrory for Governor campaign was loudly threatening to sue over a political attack ad, the campaign had quietly decided not to follow through on those threats. The ad implied McCrory was paid to lobby for tax breaks on behalf of Tree.com while he was mayor of Charlotte. A spokesman for the McCrory campaign says the threats accomplished their goal - noting the TV ad is no longer running. At one point as the attack ad was airing in late May, the McCrory campaign actually sent out a press release claiming it had made good on the threats and filed a defamation lawsuit against the Democratic Governor's Association and North Carolina Citizens for Progress. But that wasn't true. The campaign had only filed a place holder document keeping open for another month its option to sue the ad's makers. A leading defamation law expert in the state - Hugh Stevens - says such tactics are common in political campaigns. "Nothing unusual about that," says Stevens. "What would have been unusual if they had pursued the lawsuit." Stevens says defamation lawsuits over campaign ads are incredibly hard to win because the U.S. Supreme Court has accorded the highest level of protection to political speech. So, no surprise when two weeks ago the McCrory campaign let a deadline to file that lawsuit pass without following through. But here's where the story line differs from standard political threats, says Stevens: The groups McCrory threatened to sue went ahead and filed their own lawsuit to force him to back up his accusation that the ad is "false" and "defamatory." "It's a kind of put up or shut up kind of case," says Stevens, and as far as he knows, it's unprecedented among political lawsuits in the state. Stevens adds the open case obliges McCrory's campaign to respond and may even make it subject to depositions and discovery that could produce ammunition for political opponents.