Officials were investigating whether the ricin sent to Frist was connected to two earlier ricin-contaminated missives - both of which had a Tennessee postmark. So we're looking for someone who perhaps felt wronged by, and generally dislikes Republicans, is from Tennessee, and favors all-natural environmentally-correct poisons.
Scanning the mental database for someone who'd fit the bill... hmmm....
But then with the anthrax attack it was the Dims and I see there being a domestic connection