Although Smith grew up in relative comfort on the Lower East Side, he quit school and began work at the age of fourteen, after his father's death. In his political career he emphasized his lowly beginnings, identified himself with immigrants, and campaigned as a man of the people. Although indebted to the Tammany Hall political machine for his entry into politics and for their ongoing support, he remained untarnished by corruption and worked for the passage of progressive legislation. He was elected to the New York State Assembly in 1903 and his oratorical gifts and skill at drafting legislation helped him become the majority leader. When he served as vice-chairman of the commission appointed to investigate factory conditions after the disastrous Triangle Shirtwaist Company fire in 1911, he became acutely aware of the dangerous and unhealthy conditions under which many laborers worked and championed legislation to protect workers.
After serving as sheriff of New York County for several years beginning in 1915, Smith was elected governor of New York in 1918. He lost the election of 1920 in the Republican landslide of that year, but was reelected governor in 1922 and served three more terms. As governor, he became known nationally as a progressive who sought to make government more efficient and more effective in meeting social needs. His parks czar, Robert Moses constructed the nation's first state park system. During his term, New York strengthened laws governing workmen's compensation, women's pensions, and child and women's labor. In 1924 he unsuccessfully sought the Democratic nomination for president. Franklin D. Roosevelt made the nominating speech in which he called Smith "the Happy Warrior of the political battlefield."
Al Smith finally secured the Democratic presidential nomination in 1928. His acceptance speech was the first live broadcast of a political event on television, although few saw this experimental early broadcast; a great many more heard it on radio.
Smith was the first major-party Presidential candidate of the Roman Catholic faith.
A major controversial issue was the continuation of alcohol Prohibition. Smith was personally in favor of relaxation or repeal of Prohibition, but the Democratic Party refused to back him on the issue. During the campaign Smith tried to duck the issue with non-commital statements. A satire portrayed Smith being asked "Are you wet (anti-Prohibition) or dry (pro-Prohibition)?" with Smith replying "I can't rembember. Maybe I'll know better by November."
The Republican Party was riding high on the economic boom of the 1920s, which their presidential candidate Herbert Hoover vowed to continue. Hoover defeated Smith by a significant margin in the 1928 Election.
Part of Smith's especially poor showing can be attributed to anti-Catholic bias (Smith was accused of standing for "rum, Romanism, and rebellion,"), anti-New York City bias, and Smith's own bad campaigning. Smith's campaign theme song, "the Sidewalks of New York," not likely to appeal to people in Georgia, and Smith's own brogue seemed foreign to many people.
Smith felt slighted by Roosevelt during Roosevelt's governorship. They became rivals for the 1932 Democratic presidential nomination. When Roosevelt won and began pursuing the policies of the New Deal, Smith began to work against Roosevelt more. He became a leader of the Liberty League, a leading opponent of the New Deal, and supported the Republican presidential candidates, Alfred M. Landon in the 1936 election and Wendell Willkie in the 1940 election. His son, Al Smith, Jr. actually endorsed Richard Nixon in 1960.
After the 1928 election, a friend of Smith encouraged him to invest in a real estate company that was constructing the world's tallest building in New York's Midtown Manhattan. Smith was present at the ribbon-cutting ceremony when the Empire State Building opened for business in May 1931.