Marianne writes that "Differently sized constituencies mean that the party in government doesn't necessarily have the largest share of the vote." In fact, you could still get the problem even if the constituencies were all the same size. For example, if Cameron wins by large majorities in 49% of the seats and Brown scrapes in in 51% of the seats, then Brown will win the election but Cameron will have the larger share of the vote.
Marianne writes that "Differently sized constituencies mean that the party in government doesn't necessarily have the largest share of the vote." In fact, you could still get the problem even if the constituencies were all the same size. For example, if Cameron wins by large majorities in 49% of the seats and Brown scrapes in in 51% of the seats, then Brown will win the election but Cameron will have the larger share of the vote.