The Transformation of the American Party System...

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The Transformation of 1896 and the death of the third party system meant the end of America's great laissez-faire, hard-money libertarian party. The Democratic Party was no longer the party of Jefferson, Jackson, and Cleveland. With no further political embodiment for laissez-faire in existence, and with both parties offering "an echo not a choice," public interest in politics steadily declined. A power vacuum was left in American politics for the new corporate statist ideology of progressivism, which swept both parties (and created a short-lived Progressive Party) in America after 1900.

The Progressive Era of 1900–1918 fastened a welfare-warfare state on America that has set the mold for the rest of the 20th century. Statism arrived after 1900 not because of inflation or deflation, but because a unique set of conditions had destroyed the Democrats as a laissez-faire party and left a power vacuum for the triumph of the new ideology of compulsory cartelization through a partnership of big government, business, unions, technocrats, and intellectuals.
-Murray Rothbard

http://lewrockwell.com/rothbard/rothbard274.html