De Leon settled in New York City, studying at
Columbia University. He was a
Georgist socialist during the 1886 Mayoral campaign of
Henry George and in 1890 joined the
Socialist Labor Party, becoming the editor of its newspaper,
The People. He quickly grew in stature inside the party and in 1891, 1902, and 1904 he ran for the governorship of the state of New York, winning more than 15,000 votes in 1902, his best result. De Leon became a
Marxist in the late 1880s, and argued for the revolutionary overthrow of
capitalism, trying to divert the SLP away from its
Lassallian outlook. Some argue that his famous polemic with
James Connolly showed him to have been an advocate of
Ferdinand Lassalle's
subsistence theory of wages. Others question this assertion because by the same logic Marx and Engels could be described as advocates of the Iron Law because language in
The Communist Manifesto and
Value, Price and Profit pertaining to the level of wages and temporary effect of union activity on working conditions is similar to the language used by De Leon in his answer to Connolly, and the 'iron law of wages' is a Malthusian theory which De Leon did not indicate any support for. De Leon was highly critical of the trade union movement in America and described the craft-oriented
American Federation of Labor as the "American Separation of Labor". At this early stage in De Leon's development, there was still a considerable remnant of the general unionist
Knights of Labor in existence, and the SLP worked within it until being driven out. This resulted in the formation of the
Socialist Trade and Labor Alliance (ST&LA) in 1895, which was dominated by the SLP. By the early 20th Century, the SLP was declining in numbers, with first the
Social Democratic Party and then the
Socialist Party of America becoming the leading leftist political force in America (as these splinter groups embraced capitalist reforms). De Leon was an important figure in the US labor movement, and in 1904 he attended the
International Socialist Congress, held in
Amsterdam. Under the influence of the
American Labor Union (ALU), he changed his politics around this time to put more focus on industrial unionism, and the ballot as a purely destructive weapon, in contrast to his earlier view of political organization as 'sword' and industrial union as 'shield'. He worked with the ALU in the founding of the
Industrial Workers of the World (IWW) in 1905.
His participation in this organization was short-lived and acrimonious. De Leon later accused the IWW of having been taken over by what he called disparagingly 'the bummery'. De Leon was engaged in a policy dispute with the leaders of the IWW. His argument was in support of political action via the Socialist Labor Party while other leaders, including founder
Big Bill Haywood, argued instead for
direct action. Haywood's faction prevailed, resulting in a change to the Preamble which precluded "affiliation with any political party." De Leon's followers left the IWW to form a rival Detroit-based IWW, which was renamed the
Workers' International Industrial Union in 1915, and collapsed in 1925. == Personal life ==