The John Deere Classic has produced the most first-time winners of any event on the PGA Tour since 1970. Who could join that club this year?

The only player not in the mix Saturday was 36-hole leader Doug Ghim, who played his last 10 holes with two bogeys and no birdies and shot 74, pushing him outside the top 20.

Thompson made a 10-foot birdie putt on 18 to grab a 4-under 67 on a much tougher golf course for a one-shot lead.