The Conservative Party now appears to be formally against mixed member proportional. An email distributed from the Conservatives is encouraging its members to vote against MMP because, "the alternative proposed system known as MMP will increase the influence and power of the political party and its leader while decreasing the independence of MPPs." John Tory, the PC leader, also came out yesterday stating he will be voting against MMP, "because I don't think we need more politicians, because I don't think we need appointed politicians and because I think we should get on with parliamentary reform first." There are, however, prominent Tories on both sides of this debate.
The Liberal Party in Ontario and its leader, however, have been very quiet on this issue. If self-interest and power were the only guiding principles one would expect that the Tories would be the most opposed to MMP since historically they would have had the most to lose while the Liberals would have gained more over the last 50 years but not more over a shorter period of time. This may explain the Tories opposition and Liberals silence. However, there are prominent Liberals on both sides of this debate.
The smaller parties such as the NDP and Greens have strongly endorsed MMP in the Ontario referendum. The Greens would certainly be a big benefactor of MMP. The NDP believe they would also benefit from MMP, but in the longer run I am not as certain about that. There do not appear to be many, if any, prominent NDPs or Greens in opposition to MMP.