It all comes down to the bonds of trust between reporters and readers. If a publication is knowingly being used for partisan gain, it should disclose the contours of the transaction. Please understand: I am not a Pollyanna demanding that you have to identify a specific deputy press secretary or insist that every conversation with a campaign official must be on the record. It is enough to say in print something like, “Documents cited in this article were provided by Democratic sources with a partisan motivation to embarrass Romney.” Or, perhaps, “Initial guidance for this article and specific instructions on how to obtain documents were provided by Republican sources whose goal is to defeat the president in November.”

Part of the rationale for transparency is journalistic self-preservation. These days, virtually every investigative story about a candidate’s background is cynically assumed to be based on planted evidence. As oppo research comes out of the shadows (Romney’s campaign manager Matt Rhoades was a dirt-digger during George W. Bush’s 2004 reelection race), it won’t be long before campaigns start publicly bragging about story placement. In fact, it already happened in the 2010 Connecticut Senate race. GOP contender Linda McMahon claimed credit for a New York Times story documenting how Democratic rival Richard Blumenthal inaccurately portrayed himself as a Vietnam veteran. In that case, Bill Keller, then the executive editor of the Times, said, “The idea that the story originated or was sold to us by the McMahon campaign is just plain false.” But if readers never know when oppo research is the source of a story, they will always suspect that it is.

The standard argument against full disclosure of opposition research is that campaigns will not make the information available to the media unless they can do it without leaving fingerprints. Really? Do you think 21st-century campaign operatives would be so reticent about tarring their opponent that they would prefer that the information remain secret rather than be identified as the source? In truth, campaigns are using the credibility of the news media to put an imprimatur of objectivity on opposition research that would come out in any case.

In an Internet era—for those who haven’t noticed—political organizations are quite capable of self-publishing. Last week, a pro-Obama super PAC, American Bridge 21st Century, launched a website called VeepMistakes.com, which contains 1,300 pages of oppo research on three leading contenders to be Romney’s running mate (Rob Portman, Tim Pawlenty, and Marco Rubio). Of course, these items are partisan spin: (Page 345) “Pawlenty Invented His Reputation For Being Tough On Illegal Immigration.” But everybody reading the American Bridge dossiers—including reporters profiling Romney’s eventual VP—understands the political pedigree of the material.

News organizations—even in an era of parched resources—should go all out in probing Romney’s business history, especially since his career in public office is limited to just four years. (Odd how Romney has spent more of his life running for president than being governor). Obviously, Obama’s record as president is fair game as well. Ideally, the news media should do its own investigative work rather than turning to political gumshoes for assistance.

But if the Obama or Romney campaigns do get involved (and these days their political research budgets likely dwarf those of the networks and major newspapers), acknowledge the assistance in print. Truth-in-packaging is such a bedrock journalistic principle. And maybe honesty by the media (and, yes, a bit of self-flagellation) is needed to explain to the voters exactly how opposition research works in presidential politics.

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Walter Shapiro just chronicled his ninth presidential campaign. He writes the “Character Sketch” political column for Yahoo News. Follow him on Twitter @WalterShapiroPD.