there's a world of difference between CLAIMING to be open-minded and actually BEING open-minded
the worst president 'in the history of the whole wide world?' i'm guessing that you're not also claiming to have studied every presidency in the world throughout history; that would require a degree of dishonesty that would make even the most fervent 'progressive' blush-even more so than claiming to be 'open minded and to have analyzed 'all the possible variables'
so we're left with U.S. presidents. historians give far higher, if incomplete, marks to bush 2 than you do; but i realize that you are asking for opinions-in modern times, i can thing of no worse president than djimmi carter. his administration was marked by ineptitude, an utter failure to grasp world affairs and national security, and attempted, and bungled, micromanagement of the economy. i fear 0bama will be more destructive, given that he has a rubber-stamp congress that passes his initiatives without even pretending to read them, a lapdog press that spends most of its ink in abject worship and puff pieces and only 'commits journalism' when rooting thru garbage cans in search of tidbits to use in discrediting his opponents, and a cult of personality unseen outside of the former USSR