>> reporter: for the book, kesler studied his longest one to date.er in battle creek, michigan. >> the rallies are where he goes in to over drive. >> i have the greatest economy in the history of this country. >> in two hours, kesler presented as one statement presented as fact per minute. and 60% labeled as false or misleading. he bake a full-time fact can checker ten years ago. five years later, he was profiled and the team at fact check.org in a 2016 campaign, and since then, new players have entered the field. >> i brought back 700,000 jobs they brought back nothing. >> daniel, how do you rate that claim? >> everything about that claim, wolf is inaccurate. >> some. in journalism worry its not enough. a member of the new york times board, said facts are vital, but insufficient. and fact checking trump lies is essential, it's increasingly fruitless. and it was written, fact checking may make less of a difference than ever. >> with all due respect to margaret who i think the world of, i don't think she is right about that that. he has never achieved