>And what's more they've been effective in influencing what happens in parliament! It's actually not that different in practice There are a large range on view

>And what's more they've been effective in influencing what happens in parliament! It's actually not that different in practice There are a large range on views in both parties, but you put on the Democratic or Republican label in order to build a majority coalition. This is sort of like how the Westminster parliamentary system works: labor forms a government with the greens. Labor has more seats by far is and is mostly in charge, but the greens get some government positions and a little influence on the agenda of state. As a recent example of this here Bernie Sanders was not at all a Democratic party member but "joined" with them to try and get enough support.