If the mixed member proportional (MMP) system is adopted we will see a very different political landscape in Ontario. As I mentioned in a previous article, the current system encourages compromise and alliances within the party structures; MMP shifts those compromises and alliances to the legislature.
The result will be the creation of new parties and the decline, at least somewhat, of our existing parties. Take for example the Progressive Conservative Party of Ontario. It is an informal alliance of farmers, red tories, fiscal conservatives and social conservatives. It can be an uneasy alliance, in fact we saw this uneasiness split and destroy the federal Progressive Conservative Party. What happened federally also demonstrates the value of seeking out compromise and alliances within the party structure in our current system. With an MMP system one or more of these groups is likely to split off. And you will see the same thing happen with the NDP, whom I would say is an alliance of labour, environmentalists, socialists, and progressives. If the right groups split off from those two parties it will inevitably draw Liberal supporters as well. For example, the environmentalist and progressive movements would appeal to Liberals as well as the red tories.
In my last article I described a good reason why a party would not run local candidates and would only compete for list candidates. It is almost certain that some of these new parties would only compete for list candidates. The bottom line is that there is no benefit for a smaller party to run local candidates; every local candidate you win is subtracted from the list candidates you are entitled to. That will encourage alliances between parties similar to the "sister" party relationship I described. It will also distort, to some degree, what MMP is hoping to accomplish.
The end result can only be described as better or worse depending upon your own perspective. However, I believe the NDP party is the one most likely to split apart, with the Conservatives having some splitting of their base as well. The Liberals will probably become the dominant party in a new MMP system and will need to seek out the support of two or three other parties to form a majority coalition.