With his early victories in the Democratic primaries, Bernie Sanders is well-positioned to capture the Democratic nomination. It's too soon to say whether he will ultimately triumph, but it would be a remarkable turn of events in the Democratic Party. Indeed, those comparing Sanders to the party's ill-fated 1972 nominee, George McGovern, should think bigger: Sanders’s radicalism is reminiscent of the candidacy of William Jennings Bryan in 1908. Bryan shot to fame virtually overnight in 1896, when he delivered his famous “Cross of Gold” speech at the Democratic National Convention. The big issue that year was whether the United States would remain on the gold standard. Indebted farmers, especially in the South and West, were staunchly opposed to the status quo. Desperate for inflation, they sought a bimetallic standard for the currency — both silver and gold. Bryan was a 36-year-old congressman from Nebraska. Yet he had such a gift for oration that he transformed this seemingly dry policy dispute into a moral crusade. “You shall not press down upon the brow of labor this crown of thorns,” he told the delegates. “You shall not crucify mankind upon a cross of gold!” His speech created such a sensation that the convention soon nominated him for the presidency. Though Bryan had diehard followers on the Great Plains and in the Mountain West, the larger public was not buying what he was selling. Ohio Gov. William McKinley...