The magazine reported Clinton (or her campaign) was behind it.

The only basis for saying she isn't behind it is the fact that her campaign has denied it.

So its her word against the magazine's.

In such a case, you need to examine, among other factors, the history of the parties.

In the case of Clinton's staff, we have a demonstrated history of:

    A. Denials which later turn out to be false
    B. Blaming things on the "right wing conspiracy"
    C. Digging up dirt to smear opponents
    D. Other dirty tricks, including using "goon squads" to intimidate protesters.



All actions consistent with the article in question.

Furthermore, when you look at who has greater motive to lie, clearly Clinton, who is the person running for the job against Obama, has the most motive.

Therefore, based on past history and motive there is more reason to believe the magazine when it says Clinton's staff was behind.