Sorry, I wasn't clear. I didn't mean proportional to population (which yes the HOR already has) but a proporational election system in which each party receives seats proportionate to the number of votes it gets. If the Libertarian party gets 18% of the votes in a state, its candidates should get 18% of the seats of that state in the HOR.
With this system, you have political views represented in Congress that are now foreclosed by a winner take all system in which only two parties can invariably exist (for anything other than a short term spoiler role like Perot played in the 90s and Nader played in the 2000 election.
I think you are clear now, but I think it already works that way except for the Electoral College.
The smallest representative Federal element is the Congressional district thus a "Representative". If a Libertarian candidate takes a district he represents that district as a member of the state's congressional delegation, but delegations of states do not vote en-block, Otherwise our Libertarian would seem to represent a proportional seat, at least as proportional as it can be subdivided. Our Libertarian may get 90% of the vote in his district, and all the others get just over 50% in theirs, but we have no way of recognizing disproportionate enthusiasm (individual voters of a district except within the district) for any candidate other than in their representing the district they were elected from.
The "third-parties" are not well represented in the House Committee system, since those committee structures are divided into two factions for debate, and bringing legislation to the full floor for a vote. But when the House (or the Senate) is divided very closely down the middle, as it was in the last couple of years before the Ds took the house, an independent could wield a lot of power depending on the power of his or her ideas.
Now when it comes the the Electors of the Electoral "College", they are equal in number to the whole number of each states congressional delegation, but they are a seperate body from the House and the Senate. States can decide how they want their electors votes to be cast, irrespective of how other states do it, but it still would not matter in a presidential election, unless there was a very close election like in 2000.
To make a change in which a state gives up their influence without all the others also doing so across the board seems remote. So an amendment to the Constitution would need to be passed to accomplish this. Once that process begins, there will be a huge public debate, as well as an education project on both sides of the issue. It seems to be a mixed bag, but few small states would give up their unitized vote in the Electoral vote of a President along fractional lines.
I favor the present system; not for this reason but this has been the way with representative republics since the age of the Roman Republic when all 35 of the tribes stood in the Campus Martius, voted and had their votes tallied, aye or nay , winner take all accordingly. I realize that simply because it's been this way for a very long time doesn't matter much to those who seek immediate change, but if they can get an idea to catch on and spread, they can matter in elections.