All good points, @
inumbra.
I've been thinking for a long time about how our government could be made to better represent everyone's interests, and not just those interests of some special groups.
I don't think the answer to the problem of achieving full representation rests in trying to bring two politically disparate groups together. Research has shown that Conservatives and Liberals place different emphasis on different moral values. Personally, I think that this is a genetic difference, not a learned one, since it seems to originate in a person's fear response level. People who instinctively fear out-groups are going to self-sort into areas where the population density is low, and people who don't care where you came from are not going to have bad reactions to high density levels of strangers in cities and hence can make use of the greater opportunities available there. This is not to say that one response is better than the other. Disease spreads faster in cities, and strangers sometimes really are dangerous. But these differences are not something that I think are going to change anytime soon.
A better way of correcting the poor job that both parties are doing of representing the interests of average people would be to reduce the level of wealth and income inequality, since money = political power. Both parties seek money from groups that have it, since elections are presently expensive, and both parties try to appeal (by deed or by lies, whatever) to the largest number of voters, regardless of whom they actually represent.
If you make it impossible or unnecessary for a political party to gain wealth predominantly from any small group (and right now, Republicans serve the mineral extractive industries like mining and oil, while the Democrats serve the financially extractive industries like finance and high tech), then they would both be forced to appeal to the vast majority of US citizens whose needs are being completely ignored.
You could either change the laws to prevent parties from getting money from a few big donors, or you could change the law to reduce the wealth of the big donors. Either one would work.
My personal preference would be to do both, because I like living in more equal societies, and because I think that the campaign contribution law could operate as a backup for the more equal society.