It now turns out that someone leaked tax information of Christine O'Donnell of Delaware, leading to a unjustified (but newsworthy) lien on property of hers. Do you want to paint a candidate in a negative way that will cost her politically? Smear her with false claims of illegality.
O'Donnell was not a sympathetic candidate as far as most people were concerned. So what? This is America. The IRS is not a political action unit of the dominant party. When people in it break the law--and the public trust--they must be found and prosecuted. This sort of thing is not just the standard Washington, DC news leak.