AxiosNewslettersAxios ProAxios LiveAxios EntertainmentSara FischerIllustration: Sarah Grillo/AxiosThe world's biggest digital advertising companies saw significant sales growth last quarter, driving momentum for the U.S. stock market ahead of the 2024 election and foreshadowing a lucrative holiday season. The big picture: After years of pandemic-driven volatility, the global ad market is finally starting to stabilize this year.Zoom in: Investments in generative AI ad products, an influx of polit...