If he's to be consistent, David Cameron should criticise Proportional Representation for giving him a stunning victory in the European Elections in Northern Ireland, the first for the newly formed Ulster Conservatives and Unionists. (After all, he's been slagging off PR constantly for the last few weeks, and William Hague blamed PR for the BNP's two seat victory in the European Parliament elections).
It is reasonable to speculate that, if the election had been run on Cameron's First Past the Post system, Jim Nicholson, the Ulster Conservative and Unionist candidate would have come third. That was where he came in the ranking of first preferences.
But, because the election was run on the Single Transferable Vote system, a variant of Proportional Representation, Jim Nicholson came second, scoring an historic victory over the Democratic Unionist Party, who came third (they came first at the last Euro elections).
That is because the second preferences of Jim Allister of True Ulster Voice, who was eliminated in the count, went mainly, according to observers, to the Ulster Conservative and Unionist candidate, and not to the Democratic Unionist party candidate.