So does the following sound a reasonable idea instead:
Average the Dem / GOP lead and compare with lead in 2004, then halve the swing and reduce by another half if the district has an incumbent?
Personally, I would ignore national polls. They really are meaningless. It matters on a district by district basis. These districts are biased as well (more than 350 seats are in the "safe" category) so though many people want Democrats, their voices are usually slashed through and split up. I hate how we draw House districts
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