Stupidity explains a lot, in politics as everywhere else.
The evangelicals who vote for the Rats are either hung up on helping the poor, or don't understand (even now!) how far-left the Rats are. Yes, some probably vote for the Rats out of spite against Republicans who diss them, and such people are contemptible. But I think the real problem lies elsewhere. Many of these people are quite naive. And I think 25 percent may unfortunately be a low number.
I think there are a lot of blue-collar conservatives who were raised in union working families that voted Democrat from generation to generation. The loyalty is more to family tradition than to support of the real Dummie Party of today.
To vote Republican would be like slapping your Grandmother.
Family loyalty overides sensibility.
I know, I come from the same background and it's sad to see people you love who won't cross the line and vote for what is good for them.
Democrats like Hillary play to the middle to keep these people appeased.