Challenge: The Bushes as prominent Democrats

What's a most likely way, with a POD no later than 1945, to make the Bushes a powerful Democratic political family?

I'd guess it's to somehow to cause Senator Prescott Bush to break with the Republican party (a.k.a. Jim Jeffords style), but I don't know see any issue for that to happen. Maybe if he stayed in the Senate for another term (1963--69)?

But if it happened, what would be the repercussions?
 
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