But in a two-party system, inevitably each major party is a coalition of several different view points. They are tied together by common interests, including a wishing to defeat the opposing party, but wheeling and dealing goes on inevitably within any democratic political party. So a small interest group, by leveraging its power within a political party, can sometimes gain excessive power just as a minority party can gain excessive power in a multi-party system. Suppose you have a two-party system, and each party has two main factions. Then the majority faction in the majority party will run things, i.e. you can have the whole lot controlled by 26% of the legislature, provided you have party solidarity.
There’s nothing wrong with coalitions, either explicit or implicit (as you get in a two-arty system), and coalitions do not have to be short term: the Liberal-National coalition which is currently the government in Australia has existed in pretty well the same form for about 80 years, even through changes in names of the parties (the National Party used to be the Country Party, and the Liberal Party formed out of the wreckage of the United Australia Party about 60 years ago). Coalitions will last if they are based on long-term common interests, just as political parties last if they are based on long-term common interests.
It’s also worth noting that the problem of “governments falling as the result of coalitions breaking up” is a feature of Parliamentary systems, where a government requires a majority in the lower house, or some such, to function. We have a defined-terms Presidential system, where Sen. Phogbound and Rep. Delay are in office for X years regardless of whether they are a part of the Congressional majority. So the result would be shifting allegiances where Party 1 gets Party 3’s support for issues on which they agree, but Party #6’s support on other issues where Party #3 differs with them but Party #6 agrees. Add in reasonable logrolling and you have a program not far distant from what we have now, but with improved odds of a voter getting a representative who advocates his or her views. (I guarantee that Liddy Dole and Bob Edwards have neither a clue nor any desire to know how I feel about issues – all they want is a majority of Tarheels willing to support them.)
Excellent point. For instance, in the past 20 years the Religious Right has gained a lot of influence within the Republican Party – in some localities it completely dominates the local party organization. Yet it does not get as much influence at the national level as it thinks it deserves – no Republican president has really pushed hard for banning abortion or reviving school prayer. Meanwhile, voters who want to vote Republican for reasons of economic policy, but who do not agree with the Religious Right’s social agenda, have to take what is, in their eyes, the bad with the good. It’s rather frustrating for all concerned. If we had a system where the Religious Right could break out of the Republican Party and go its own way, that would be better, more satisfying, for both economic conservatives and social-religious conservatives. They would each have their separate representative party and they would have to work together only on issues where they actually are in agreement.