On September 1, the Post published a column from Thiessen criticizing the idea of former Massachusetts Gov. Mitt Romney running for president again in 2016. In the piece, Thiessen identified Scott Walker as one of several “successful governors” that would be a preferable candidate. Thiessen co-authored Walker’s 2013 book, a fact the columnist has previously disclosed when writing about the governor for the Post but which went unmentioned in his latest column.