Our winner take all political system can only ever support two parties. If the GOP blows up then they, or their further right wing counterpart party, will never win another national election. Or at least not until several years pass and one of those parties absorbs the other in the name of being able to win elections again. That would essentially just recreate the Republican party again. It's a pretty well-known feature of winner take all election systems that they tend toward two party systems. In order to have more viable parties we'd have to have large scale reforms that would make both parties less powerful.