Ellen Burstyn is
Barbara Bush
Requiem for a Dream should have left Burstyn with all the cinematic training she for scenes where Barbara's son, the young Dubya, battles drink and drugs. Perhaps her role as the matriarchal Sister Summerisle in The Wicker Man remake will also prove useful, since Barbara is generally regarded as a formidable personality who rules her roost with a firm hand (albeit one who has never engaged in human sacrifice. That we know of).