The Senate is appointed by a state's legislature and not directly elected by the electorate, with each term lasting six years, whereas representative terms run for only two years. With the benefit of more time, the Senate is more stable meaning that decisions can be followed through on; this also has its pitfalls meaning that Senators don't reflect, always, the current mood of the country. With that said, I think that the Senate should have relatively more stability than the House of Representatives, but perhaps, should be re-elected every 3 years, not 6.
Because it's always only been about these 2 parties. Republican and democrat. The third parties are just there... they never ever get enough votes to win, electoral or popular vote.
