That depends on what you mean by fringe groups. The Green Party on the left and the Libertarian Party on the right get a lot of grief for taking votes from the major party candidate they are closest to and helping to elect the one they are farthest from, but some of the most thoughtful people on both sides, with the sincerest and most reasonable opinions, have been from these so called third parties. Countries with much smaller populations than we have function with more than three parties. The problem with both major US political parties is that the leadership is focused on keeping and expanding power. There are plenty of sincere voters at the bottom, and some sincere small time candidates, but at the top it us all about money and power. Down with the Republicans, down with the Democrats, up with reasonable people of all political philosophies.