Carrol, these characters work as a team. You've got your crazies like McCarthy (and his predecessors - he wasn't the only right-wing anticommunist in American history) and then the Dems can seems like sane, reasonable alternatives to them.
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Partly, it's my own memories, even my own experience. It's true Truman vetoed Taft-Hartley, but it took DP votes to pass it over his veto -- with its _highly_ effective expulsion of Reds from the CIO. And before that, there was Reuther's red-baiting defeat of Thomas for the UAW presidency. State loyalty oaths for teachers were also independent of Joe's shenanigans.
The Red Hunt was inseparable from the launching of the Cold War -- not McCarthy's concern.
There were right-wing crazies on HUAC -- but the whole Congress kept supporting it.
A Time magazine column warned Red hunters not to plague the Socialist Party. Why? Socialists were skilled in fighting Reds.
Carrol