Most people in the US do not identify themselves as either Republican or Democrat (see Gallup data).

[![enter image description here](https://i.stack.imgur.com/NWnOq.png)](https://i.stack.imgur.com/NWnOq.png)

There seems to be four possible explanations. 

1. These independent-leaning Americans prefer more far-right policies. But this seems unlikely, since the Constitution Party gets a microscopic amount of votes compared to the GOP.
2. These independent-leaning Americans prefer more far-left policies. This too seems unlikely, given the amount of votes won by the Green Party.
3. Most Americans are not fond of the current left/right political spectrum. Rather they'd prefer a completely radical approach to the economical and political system of the land. This seems more likely than the others, but still dubious, given that most Americans probably have little clue of the feasibility of the proposed solutions. Either way, the Libertarian Party and the Party for Socialism and Liberation (capitalists and communists, respectively) don't get all that many votes.
4. Most Americans are somewhere in the middle of the left/right political spectrum and do not feel represented by either of the two major parties as the Republicans can tend to be far too right and the Democrats can tend to be far too left. This seems like the most likely explanation, or at least the most simple.

Given that, why are there so few serious attempts at creating a third mass-appeal party that is more central on the political spectrum? The other 3 explanations above already have their dedicated parties: Constitution Party, Green Party, Libertarian Party, etc... but there doesn't seem to be any serious attempts at creating a central party? 

Decades ago, perhaps, such a party would have been unnecessary, since it would have overlapped with the GOP and the Democratic Party. But now that those parties seem to have become more extreme and the public seems to have become more independent-leaning than ever, surely such a new party would have a lot of potential?