In June 2023, YouTube decided to stop fighting the most persistent strain of election misinformation in the United States: the falsehood that President Joe Biden stole the 2020 election from Donald Trump.

Within months, the largest video platform became a home for election conspiracy theories, half-truths and lies. They in turn became a source of revenue for YouTube, which announced growing quarterly ad sales Tuesday.

During four tumultuous months of this year’s presidential campaign, researchers from Media Matters for America, a group that monitors information from conservative sources, examined the consequences of YouTube’s about-face.