Opinion polls are also known to be entirely incorrect when predicting the outcome of certain events. The best-known example of this is the 1948 US presidential election, in which the prediction was that Thomas Dewey would easily defeat Harry Truman. Major polling organizations, including Gallup and Roper, indicated a landslide victory for Dewey when, in fact, Truman was the victor in a close election and kept the presidency. 2016 saw the validity of opinion polls enter the debate once more, as polls in both the UK "Brexit" referendum and the US presidential election were ultimately shown to be largely incorrect. Polls widely predicted a win for Democratic candidate Hillary Clinton, while instead Republican candidate Donald J. Trump won the Electoral College and, therefore, the presidency.