"Fact checking" of the statements of politicians (and other political agents) in debates and other public venues has become a major thing in the past decade or so (interestingly, many professional journalists used to object to "fact checking" the statements of those they covered on the grounds that their job was to accurately report what people said, not to determine whether or not it was true). The 3 most established fact checkers, monitoring the factual accuracy of what is said by major U.S. politicians, are:
Other sources: