During a “Late Show” appearance, Colbert said heis thinking seriously about a challenge to Trump.
ref:https://www.washingtonpost.com/politics/holder-says-hell-decide-about-a-2020-presidential-bid-early-next-year/2018/07/24/d6f7135c-8f34-11e8-bcd5-9d911c784c38_story.html