"Taft's weight continues to be an object of public fascination: the Washington Nationals recently added Taft to the pantheon of "racing presidents" who scamper about to entertain the crowd, because he is credited with having started the tradition of the seventh-inning stretch as well as throwing out the first pitch in 1910. The Taft mascot was nicknamed "Big Chief," according to the Washington Post, and was made "a bit larger" than his polyurethane colleagues".

The above is from page 12 of "WILLIAM HOWARD TAFT" by Jeffrey Rosen.