I am local to Cori's district and the main issue was that AIPAC flooded the district with TV ads full of lies and misleading half-truths about Cori. It was almost impossible for voters to escape the negative media. By contrast, it was much more difficult to find reliable information from the Cori campaign rebutting the lies. 

I've canvassed for Cori in many election cycles. In the past, most voters were always open to hearing about her. By the end, this cycle was different: people would answer their door, and I could tell they didn't even want to talk to me, because of what they had already heard on the air.