As every U.S. schoolboy knows, and some of his elders forget, the two-party system is not as old as the Liberty Bell.* But, as every practicing politician knows, no third party has seriously challenged the two major parties since the Civil War.
In the nation's clamorous early years, parties grew, split and withered like excited amoebas. Hamilton's Federalists and Jefferson's Republicans faded away, and the Whigs and the Democrats took their place. Splinter parties were formed on such frenetic issues as a fanatical prejudice against Masons (the Anti-Masons), or a dislike for...