But our system guarantees we'll always have one. Not just the two houses of the legislature, but each state has 2 houses.
It would only be a matter of months before a multi-party system would fall into a 2 party system again. Coordinating 50 legislatures with 1 federal is a giant task. Even if you had a bunch of libertarians from Montana, to get anything done at the federal level, they'd have to work with the Christian conservatives from the south east. it wouldn't take long before they're voting for each others stuff in lock step, and when that happens, (as it has in real life) there is no difference between the two groups.
