On Monday, The Wall Street Journal reached a bold conclusion on one of the central debates of the 2012 elections: “Super PAC Influence Falls Short of Aims,” declared its front page, above-the-fold headline. “The flood of spending doesn’t appear to have significantly influenced voter opinion in key states in the presidential contest,” the story asserted.

The report detailed heavy ad buys by conservative super PACs in contested states such as North Carolina, Michigan, and Pennsylvania. It noted the stubborn deficits that Romney faces in voter opinion polls in these battlegrounds. By way of pushing back on its own hypothesis, it dutifully quoted super PAC directors arguing that if it hadn’t been for their efforts, the presidential race might not have remained competitive through the summer.

But what the story didn’t provide was evidence to support its central claim: that super PACs were not having a substantial influence on voter opinion.

Instead, it relied almost entirely upon a circular premise: Conservative super PACs have spent heavily on the presidential race in certain states, and Mitt Romney has performed poorly in polls in these states, so therefore the super PACs have failed to influence voters.

It ain’t necessarily so. “You can’t say his failure to close the gap shows the ads aren’t effective,” said Michael Malbin, executive director of the Campaign Finance Institute and a political science professor at SUNY Albany. “They’re running ads at a time when the candidate is off in London putting his foot in his mouth.”

It is always difficult to isolate the role of individual variables in a scenario as complex as a presidential campaign, where the quality of candidates, the flow of current events, and both campaign substance and campaign gaffes can all have an influence on voters. That does not mean that journalists should avoid drawing out factors such as super PAC spending, but that they have to be careful about linking cause and effect.

There are a number of questions that the Journal could have addressed that might have put its premise to the test. For example, numerous voter opinion polls have been conducted in swing states before and after significant ad runs by super PACs. Did the numbers change over a period of heavy ad saturation? Did they change on the issues specifically addressed in the advertisements?

The Journal also cited speculation by observers that viewers may be skeptical of ads by third parties, or may miss them altogether because they watch TV content online, or record it and fast-forward through commercials. Maybe. But has anyone studied whether viewers are more distrustful of outside ads? What do statistics or industry experts say about how often TV ads are getting tuned out?

Given the intense debate surrounding the impact of outside spending—much of which is still yet to come, and some of which will be aimed further down the ballot, to Senate and House races—the Journal is right to examine its role. But a front-page story with declarations as strong as this one— that super PACs have failed to perform as expected—should be able to back up its assertion with new evidence.

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Sasha Chavkin is an investigative journalist based in New York City. He has written for ProPublica, the Center for Public Integrity and the New York World. Chavkin's reporting on the ad wars in campaign 2012 is supported by the Toni Stabile Center for Investigative Journalism at Columbia University's Graduate School of Journalism.