More than $1.6 billion has been spent or booked on TV ads in a dozen Senate races, with $3 out of every $4 being spent in six states — Georgia, Pennsylvania, Arizona, Wisconsin, Nevada and Ohio, according to an NPR analysis of data provided by the ad-tracking firm AdImpact.Outside groups, including those closely tied to Senate Minority Leader Mitch McConnell, have poured in nearly $1 billion to buoy GOP Senate candidates. Eighty-six percent of the money going toward pro-GOP TV ads is coming from these outside groups, compared to 55% for Democrats.This episode: voting correspondent Ashley Lopez, political correspondent Susan Davis, and senior political editor and correspondent Domenico Montanaro.Support the show and unlock sponsor-free listening with a subscription to The NPR Politics Podcast Plus. Learn more at plus.npr.org/politics Connect:Email the show at nprpolitics@npr.orgJoin the NPR Politics Podcast Facebook Group.Subscribe to the NPR Politics Newsletter.