The Republican Party was born in 1854 as a coalition of opponents to the expansion of slavery across the continent, and took its name as an homage to Thomas Jefferson's vision of a decentralized government with limited powers. By 1860, when its standard-bearer, Abraham Lincoln, won the White House, it had displaced the Whigs as the chief political opposition to the Democrats.

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Democrats also lay claim to Jefferson. The party formed out of opposition to Alexander Hamilton's Federalist Party fiscal policies, which Democrats said favored banks and wealthier Americans. Jefferson became the first Democratic presidential candidate when he ran -- unsuccessfully -- for office in 1796. He later became the third president and served two terms starting in 1801.

The Republicans saw success in the 1870s, but the period also spawned factions within the party. William McKinley’s election in 1896 was viewed as a resurgence of Republican dominance. The party’s pro-business policies of the 1920s seemed to generate an unprecedented prosperity –- until the Wall Street crash of 1929 ushered in the Great Depression.

Still regarded as the party of big business, the Republicans grew in strength in the 1960s and 1970s when many conservative southern whites abandoned the Civil Rights-supporting Democrats. In the 1980s, under President Ronald Reagan, that strength was fortified as the party became the home for conservative Christians eager for the political power to advance an agenda that included ending abortion rights and halting gay marriage.

Led by Rep. Newt Gingrich, R-Ga., the Republicans won control of Congress in 1994, ending three decades of Democratic power. When George W. Bush won the presidency in 2000, the party controlled Congress and the White House. But by 2006, a seemingly endless war in Iraq and a growing number of corruption probes helped the Democrats recapture Congress. Whether the Republican nominee, John McCain, can retain Republican control of the White House in 2008 remains to be seen.