When you read a negative story about a political candidate that doesn’t seem all that important, it’s likely that story came from a competing candidate’s negative research team, who leaked it to a journalist they had reason to believe is an ally. This is the only way I can explain a page-one story in last Wednesday’s New York Times about an investment Barack Obama made in late February, 2005. Times reporters Mike McIntire and Christopher Drew say Obama bought more than $50,000 worth of stock in two companies whose major investors included some of his large political donors; one company was a biotech concern starting to develop a drug to treat avian flu. Two weeks after buying about $5,000 of its shares, write McIntire and Drew, Obama took the lead in a legislative push for more federal spending to battle the disease. A spokesman for Obama said the Senator didn’t know he had invested in either company until several months later – his broker had bought them without consulting the Senator, under the terms of a blind trust – and when Obama learned of the investments he sold them, at a loss of $13,000, in order to avoid even the appearance of impropriety. Yesterday’s (Thursday’s) Times contains another story, this by Christopher Drew and Jeff Zeleny, repeating the Thursday story, but adding that “Obama faced a barrage of questions about his investment Wednesday after a Washington news conference about immigration.”

The Wednesday page-one story is not really a story. That Obama’s stock broker bought $50,000 of stock in two companies whose investors included some of his large political donors raises no conflict of interest issue, even if Obama knew about the transaction. That he pushed for a drug to treat avian flu and had put $5,000 in a firm that was developing a vaccine for it might suggest he sincerely believes in the importance of developing such a vaccine, and could create the appearance of a conflict of interest, but note that Obama sold the stock long before the story broke, so he must have been sincere in his desire to avoid any appearance of impropriety.

The Thursday story, referencing the “barrage of questions” Obama faced on Wednesday about these transactions, is also not a story. There was a barrage of questions only because the Times had put the story on its front page on Wednesday, thereby creating the barrage.

So what’s going on? Dirt-digging researchers on the staffs of one of the other major Democratic candidates – either Edwards or Clinton – came up with this stuff, and leaked it to Christopher Drew. Your assignment: Figure out, on the basis of Drew’s past coverage of Clinton and Edwards, which candidate was more likely to do the leaking because he or she believed that Drew would take it and try to get it high prominence in the paper.