The Two-Party System Under Pressure

The United States is one of the few Western democracies that has retained a two-party system for much of its history.  Sure, the names of the parties have changed from time to time and the political values espoused by the major parties are often unrecognizable from what they were generations ago, but the occasional flurries of interest in third parties have invariably crashed and burned.  We're witnessing another one of those periods of pressure on the two-party system now and one wonders if this time the results might be different.