The GOP could lose Senate races in Pennsylvania, Illinois, Wisconsin, New Hampshire, North Carolina and Missouri, which would end two brief years of Republican control of Congress. Senate aides say "the reason we don't hold the Senate, if we don't, is because of Donald Trump."
“What has to sting Republican strategists most is that they have the opposite problem in 2016 that they had in 2012.” Trump is polling five points behind down-ballot GOP candidates, whereas Romney polled five points ahead.
The GOP is closing the spending gap, but because their ad dollars are being spent so much later in the game, ad time is more expensive, and they’re getting less bang for their buck.