update 10/18/18
From this article:
“Republicans pushed negative messages in nearly six out of 10 of their recent television ads, unleashing sharp and often intensely personal attacks on Democrats as the party scrambles to retain its House majority, a CNN analysis shows.”
Half of Senate Ads Negative in Past Month
from the analysis:
“Overall, Democrats have been much less negative in 2018 than Republicans. While 37 percent of ads supporting Democrats were negative during the September 4 to October 1 period, 59 percent of ads supporting Republicans were negative. ”
update 10/25/18