At least in US history, the "change" in parties is a rapid upheaval where one party is largely replaced by another, leaving the country with a two-party system -- just one with a different party. Third parties don't work here because they take their voters primarily from one side or the other and voters typically decide that it's better to vote Republican than to split the vote with a Libertarian candidate and risk a Democrat taking the seat (or vice versa with the Green party and Democrats). There's no magical "Centrist" party that appeals equally to both sides of the divide.
In my opinion, it's a part of the problem with the system. We have an all or nothing system which makes 49% of votes not seeing a return, a number which would be even higher if there were more parties. If we were interested in making a more smooth political system (ie. less of the edge effects that lead to a wholly adversarial system) which would put more weight on compromise plans, we could shift that. Right now, 51% of the votes make 100% of the decisions whereas a more proportional representation system (ie. 51% has 51% of the power) would favor a larger number of parties meaningfully taking part in the political process. Unfortunately the design of such a system is tricky, because you have to be more able to quantify qualitative things.