> A lot of people would argue that they're both middle ground parties that pretend to have big differences for the show of it.
Even though a lot of people argue that, if it weren't true things would be far worse. Despite the differences, there needs to be something resembling a governing consensus.
We do have centrist parties in general elections. The non-centrist tendencies arise in the primaries. Then the non-centrist primary voters get miffed after the general election on account of the centrist lurch to collect independent votes.