Could have been a great-ish film
...even with the same cast and same script. But Ranald MacDougall, normally a screenwriter, was a first-time director and he was basically hapless with the camera and the actors (although Crawford, obviously, didn't need direction).
Would have been nice to have seen the film handled by a competent director.
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LBJ's mistress on JFK:
https://www.youtube.com/watch?v=WcXeutDmuRA