The "Chicago Daily Tribune", a pro-Republican newspaper, was so sure of Dewey's victory that on Tuesday afternoon, before any polls closed, it printed "DEWEY DEFEATS TRUMAN" as its headline for the following day. Part of the reason Truman's victory came as such a shock was because of uncorrected flaws in the emerging craft of public opinion polling. According to historian William Manchester, "many professional pollsters...believed in what some had come to call Farley's Law." James Farley, President Franklin Roosevelt's successful campaign manager in 1932 and 1936, had stated that, in his opinion, the great majority of voters decided which candidate to support during the political conventions. The fall campaigns, Farley believed, were simply "ineffective carnivals" that swayed few voters. In 1948 many pollsters, relying on Farley's Law, believed that the election was effectively over after the Republican and Democratic Conventions, and they discounted the impact of Truman's campaigning that fall.