The USA is a 1-party dictatorship in the guise of a multiparty Democracy. The Republicratic Party puts on show elections to bamboozle the public into supporting them (although occasionally, somebody who isn't a "centrist" gets nominated, in which case his own party revolts and he is defeated in a landslide; this happened in 1964 and 1972, but probably won't happen again, as the fates of Ron Paul, Dennis Kucinich, and Mike Gravel in the 2008 election show). In the past, both candidates ran on virtually identical policies. Nowadays, as Americans grew increasingly disgusted with big government and its wars in the 1960s and 1970s, the "Republican" pretends to be for limited government and the "Democrat" pretends to be for peace. However, once those pesky elections are over, the charade is up and both parties vote for bigger government and for wars and those opposed to expanding government are smeared as advocates of "polarization" and "divisiveness" and said to be opposed to "bipartisanship" (a more accurate thing to say is that "extremists" believe that the voters ought to be allowed to choose policies instead of merely pretending to choose).
It wasn't always this way. In the 19th century, America was a 2-party democracy and sometimes a 3-party or 4-party democracy (with the exception of a few years during the Monroe Administration). The parties stood for diametrically opposed ideas and Americans were much more enthusiastic in their support for parties. Each party published its own newspapers in each town, promoting the party line. This changed in 1896 when the Democratic Party was turned into a carbon copy of the Federalist/Whig/Republican Party following the Bryanite hijacking of that party. However, there would be an exodus of old Democrats to the Republican Party in the early years of the 20th century, which kept somewhat of a democratic political system in existence. From 1920-1928, America was ruled by Republicans who believed in the laissez-faire ideology of the 19th century Democrats, although Herbert Hoover, of the party's "left" wing became president in 1928 and began the New Deal. Many Republicans, however, opposed this and the Republicans remained somewhat of an opposition party until the early 1950s. At this time, CIA agent William F. Buckley Jr., the son of an "Old Right" Republican, created the "conservative" movement that destroyed the "Old Right," creating a permanent 1-party system.
Ironically, the Military-Industrial Complex's growth began around 1950. Today, it, along with Big Business, Big Labor, Big Religion, and others virtually control the nation's political system.
Personally, I don't think the charade will last much longer. Most Americans can now see the Republican Party for the fraud it is (including most who vote Republican; they don't like Republicans, they merely are against the Democrats). Soon, most Americans will see the Democratic Party for the fraud it is and then the game will be up for the elite.