So a few words about Wallace.
Though I agree his presidency would have been disastrous, I have to point out that he was a far better man than much of this board seems to believe.
Wallace's views about the Soviet Union were shared by much of the American political elite during the Second World War, and even FDR had a fairly sanguine view of Stalin. There wasn't any doubt that Stalin was a dictator, but many took a fairly benign view of him, believing that rising living standards would ultimately bring the Soviet Union a more democratic government, and that central planning innovations could have use in the West.
Wrong? Sure. But it wasn't an uncommon view in those days.
Moreover, on domestic policy, Wallace was basically a Great Society liberal who came around two decades too early.
I suspect a Wallace presidency would have been disastrous, as, yes, many of the people he appointed would have turned out to have Soviet ties or Soviet agents. Wallace was no fool, and though he would likely have ultimately seen Stalin's duplicity, the cost of the delay to his political reputation would have been disastrous.
But again, Wallace was no fool. He himself repudiated the Progressive Party in 1950, wrote a book declaring he had been wrong about the Soviets, and then endorsed Ike in '52 and '56.