Former U.S. Rep. Gabrielle Giffords is assisted by her husband, U.S. Navy Captain Mark Kelly (R) prior to a Senate Judiciary committee hearing on gun violence in January 2013. (REUTERS/Kevin Lamarque)

The conventions of political journalism furnish a tried-and-true way of proving that a given politician has overstepped. You see it all the time: Even so-and-so’s allies are expressing displeasure with so-and-so’s tactics.

This evidentiary trick surfaced in a Politico story earlier this week titled “Gabby Giffords gets mean” under the byline of reporter Alex Isenstadt. Victim of a shooting at a “Congress on Your Corner” event in January 2011, former congresswoman Giffords is now orchestrating political advertising through her gun violence prevention super PAC Americans for Responsible Solutions.

And she’s being mean about it! As Isenstadt reported, that’s a matter of consensus: “The former Democratic congresswoman, whose recovery from a gunshot wound to the head captivated the country, has unleashed some of the nastiest ads of the campaign season, going after GOP candidates in Arizona and New Hampshire with attacks even some left-leaning commentators say go too far.”

That’s just the sort of allegation that requires a great deal of substantiation within the four corners of a piece of journalism. At least a couple — preferably three or four — liberal detractors need to be quoted to establish the notion that Giffords is out of control on gun control. Politico cited almost one: “On Friday, the Arizona Republic’s editorial page, which is typically liberal leaning, called a [Giffords-sponsored ad] “base and vile.”

One very outspoken Twitter user tapped out some skepticism in the direction of Rosslyn:

And what about the endorsement choices of the Arizona Republic?

Here’s an excerpt from its October 2012 presidential endorsement: “Mitt Romney, certainly, would not a perfect president make. But he is far, far removed from the grotesque caricature of the heartless plutocrat created by the Obama campaign and its allies. Democrats from Bill Clinton to Cory Booker defended Romney’s work at the much-maligned Bain Capital for a reason: because it has been financial engines like Bain that have helped power the American economy. America needs a return to that kind of economic power, that kind of jobs-creating energy. The nation’s best chance for reviving those spirits lies with Mitt Romney.”

To its credit, Politico issued a correction to its characterization of the Arizona Republic’s editorial orientation:

CORRECTION: An earlier version of this story characterized The Arizona Republic’s editorial page as “left-leaning” and “typically liberal leaning.” The paper has endorsed members of both parties, including recent Republican candidates for president.

With that, the story’s linchpin dropped to the ground. Not only didn’t the piece cite “other” left-leaning voices hammering Giffords’ alleged mean streak, it didn’t cite any such right-leaning voices either, save for that of GOPer Martha McSally, who is seeking Giffords’ former seat. McSally called the ads “false and malicious,” as Isenstadt reported. Other Republicans, noted Isenstadt, “want to hit back, but it’s quite the conundrum going after Giffords.”

Another possibility is that these “nastiest,” “mean,” “bare-knuckled” tactics from Giffords’ group really aren’t all that nasty, mean and bare-knuckled. “To be honest, we haven’t really gotten much criticism at all,” says Pia Carusone, senior adviser of Americans for Responsible Solutions.

Though the correction did violence to the premise of the story, Politico is holding onto it with this language: “The former Democratic congresswoman, whose recovery from a gunshot wound to the head captivated the country, has unleashed some of the nastiest ads of the campaign season, going after GOP candidates in Arizona and New Hampshire with attacks even some longtime supporters say go too far.” Those “supporters” are apparently the Arizona Republic, which “has previously endorsed Giffords,” according to the corrected piece.

Judge the level of meanness for yourself:

Erik Wemple writes the Erik Wemple blog, where he reports and opines on media organizations of all sorts.