Robert A. Slayton is a professor of history at Chapman University and the author of “Empire Statesman: The Rise and Redemption of Al Smith.”

WITH Mitt Romney, a member of the Mormon church, quite possibly heading toward the Republican nomination, Americans may be faced with a presidential aspirant whose faith many find strange and troublesome. It would not be the first time that has happened, and during a previous campaign the response was pretty nasty.

By any measure, Alfred E. Smith, the Democratic candidate against Herbert C. Hoover in 1928, had a formidable record. Growing up poor, Al (as everyone except The New York Times called him) left school at age 12 to go to work, at jobs that included a stint in the Fulton Fish Market.

An outgoing lad with a fine speaking voice, he gravitated to street corner politics and on to Tammany Hall. Smith started as an unknown member of the New York State Assembly and rose to become speaker. In 1911, he led the investigation of the Triangle shirtwaist factory fire and sponsored the subsequent reform legislation that influenced fire codes nationwide.

Like Mr. Romney, Smith was the governor of a northeastern state. He served four nonconsecutive terms beginning in 1919, and a good argument can be made that Al was the greatest chief executive in the history of New York State, where he created the precursor of the New Deal.

So Smith should have been an impressive candidate, but the electorate had several problems with him. Voters reacted to his equivocal stance on Prohibition, to his Irish heritage, even to his New York roots. Their foremost objection by far, however, was to his religion: Smith was a devout Roman Catholic....