The claim that St. Louis Circuit Attorney Kimberly Gardner is backed by George Soros is true. Soros currently supports and has previously supported Gardner financially by funding her election campaign in 2016 as well as her re-election campaign in 2020.
According to “Meet Kimberly Gardner, the Rogue Prosecutor Whose Policies Are Wreaking Havoc in St. Louis” by Zack Smith and Charles Stimson for The Heritage Foundation, “Like many other rogue prosecutors around the country, she was swept into office by winning her 2016 election with a wave of money from George Soros and tech billionaire-funded entities, who again contributed heavily to help her win reelection in 2020.”
It was difficult to find the exact value of Soros’ financial support but in an article titled, “Follow the money: Soros pumps $116K into St. Louis prosecutor's campaign and other donations of note,” by Christine Byers for KSDK News, “New York-based billionaire George Soros pumped $116,000 into the Missouri Justice & Public Safety Political Action Committee, which is supporting Gardner.” While the financial support doesn’t seem to be going directly to Gardner herself, records indicate Soros is financially supporting organizations directly linked to Gardner. It was incredibly difficult to find exactly how much Soros has given to Gardner’s campaign but according to the KSDK article, Soros is no stranger to financial backing with previous donations going to Cook County State’s Attorney Kim Foxx for $2 million and almost $4 million to political action committees in support of prosecutors in Arizona, Colorado, Florida, Georgia, Illinois, Missouri, New Mexico, Texas, and Wisconsin.
https://www.heritage.org/crime-and-justice/commentary/meet-kimberly-gardner-the-rogue-prosecutor-whose-policies-are-wreaking
https://www.ksdk.com/article/news/crime/byers-beat/campaign-donations-st-louis-local-2020-races/63-bdeaccfe-0cde-43a5-9e5f-72979725cb88