Data: AdImpact; Note: Includes video ad spend and reservations by campaigns and outside groups; Chart: Erin Davis/Axios Visuals
Republicans are going all-in on Ohio this month while Democrats give the Arizona race a major boost in what is expected to be a nail-biter fight for control of the upper chamber.
Why it matters: Senate campaigns are plotting their final bets on what they see as their path to another two years of Majority Leader Chuck Schumer (D-N.Y.) or a new era of GOP leadership and control.
Compared to August, Republicans are set to spend 2.4 times as much on video ads this month to back Bernie Moreno's bid for Senate, according to AdImpact.
Democrats have also more than doubled their ad spend in support of Ruben Gallego in Arizona, who is running against Republican nominee Kari Lake, who has repeatedly cast doubt on the 2020 election results.
Between the lines: This is just based on buys and reservations made as of Sept. 16 — new ad buys are happening all the time and more could come in the final weeks of the month.