I think it's worked in different ways. In the early years what happened is when people voted for a party, they'd vote for, really, all the candidates of that party; they'd vote very much on party lines and wouldn't vote for the other big party.
Nowadays, it's much more mixed, so I think what we see in the results—and the electoral system facilitates that being translated into seats—is that people think rather less of those parties than they used to and even though they might vote for a candidate from one of those parties, they don't, to anything like the same degree, support all the candidates of those parties. They may be a little more candidate-centred than they used to be. If that's what the voter wants, then democracy said that's what the voter should get.