With less than six weeks left until Election Day, and early voting already underway in some states, U.S. campaign ad spending levels continue to astonish. Here’s what you need to know right now:

• Total campaign ad spending for U.S. Senate, U.S. House, gubernatorial and other key races in the U.S. midterm elections has surged past $3.7 billion, according to the latest Ad Age Campaign Ad Scorecard analysis. (Campaign Ad Scorecard is part of Ad Age’s Campaign Trail coverage, a project of Ad Age Datacenter, led by Director of Data Management Kevin Brown in partnership with Kantar/CMAG.)

• That $3.7 billion total includes TV, radio and tracked digital advertising (from Dec. 28, 2021, through Election Day, as of Sept. 26, 2022). Scroll down for our in-depth charts.

• To give you a sense of the pace of spending, that total is nearly $700 million more than the figure ($3 billion) we reported in a Campaign Ad Scorecard we published on Sept. 1.

• The most expensive race this midterm isn’t for an elective office—it’s for an issue: sports betting in California. There are two different ballot initiatives—Proposition 26 and Proposition 27—on the ballot in the Golden State related to sports betting. The latter is a measure to allow online sports betting, while the former has to do with legalizing sports betting on American Indian lands, primarily at casinos. More ad dollars have been spent (or booked) for (and against) Proposition 27 than for any other contest. Combined, spending on pro- and anti- advertising for both 26 and 27 now totals $314.3 million, per Ad Age Datacenter’s analysis.

• Notably, big national brand marketers in the gambling space—DraftKings, FanDuel and BetMGM—have been pouring money into the coffers of the pro-27 groups.

• The most ad-soaked, spendy race in the country involving specific politicians is the U.S. Senate face-off in Georgia, where Republican nominee (and former football star) Herschel Walker is trying to replace incumbent Democrat Raphael Warnock. Republicans and Democrats—including the candidates’ campaigns and the PACs supporting them—have spent a combined $203 million on ads surrounding the race.

• It’s worth noting that all five of the most expensive races in the country involving specific politicians are about U.S. Senate seats—in Pennsylvania, Arizona, Nevada and Wisconsin, in addition to Georgia. For now we’ll just focus on the high-profile Pennsylvania race, which pits Republican nominee Mehmet Oz, the celebrity doctor and former TV host, against John Fetterman, the Key State’s lieutenant governor. Republicans and Democrats—including the candidates’ campaigns and the PACs supporting them—have spent a combined $175.1 million on ads surrounding the race. Scroll down for more specifics.

• Gubernatorial races, including the Texas face-off between Democrat Beto O’Rourke and incumbent Republican Greg Abbott, round out our top 15 list of the most ad-soaked, spendy races in the country. O’Rourke vs. Abbott is actually a relatively economical race, with a combined ad-spending total—by Republicans, Democrats and the PACs that support them—of $47.8 million. Scroll down for more specifics.

• Incidentally, as of this writing, poll-parsing site FiveThirtyEight says that “Republicans are slightly favored to win the House” and “Democrats are slightly favored to win the Senate,” per a statistical model that simulates the election in each chamber 40,000 times. Keep reading here.