Assuming, of course, that that was the desired end. This assumption fails to take into account that personages such as Daschle and Brokaw never open their own mail. It isn't rocket science to figure out that "targeting" Daschle or Brokaw in this manner would be futile, if the intent was to kill them.
No, the logical rationale would be to "fire a warning shot" at them. In Daschle's case it's rather elementary as to why he would be targeted in this manner. As Senate Majority Leader, and current political head of the Democratic Party, he, and he alone, could put the brakes on any initiaives by President Bush against Al-Qaeda, or others...
the infowarrior
And targeting him in a predictably ineffective way would make him much less likely to oppose any such initiatives. If, as I suppose, the Islamofascists are behind these anthrax attacks, they were supposed to help provoke a massive U.S. military response, just as I think Sept. 11th was.