Somebody: Within the parameters of bourgeois democracy, we live in a free country. Americans have every opportunity to build new parties and movements in opposition to the status quo, but they resolutely refuse to do so. Somehow they found the time for such endeavors in the 19th century, but are too over-worked to do so today. I take it for granted here that the Tea Party is primarily a right-wing pressure group or faction of the Republican Party.
Whatever the reasons, bourgeois democratic systems are characterized by a trend towards party stabilization over time. Only in new democracies, like in Eastern Europe in the 1990's, do you see of high frequency of new political parties emerging. In the U.S. this is compounded by our majoritarian system and lack of proportional representation. The British people may be disgusted with Labour, the Tories, and Lib Dems, but it's unlikely any new parties will emerge to contest them, the same holds true in Germany, France, and most other industrialized nations.