One unintended consequence of KD's proposed restrictions is that it would appear to limit the efforts of a third party to gain traction and grow. For a third party to grow, they need to 'colonize' states where the party doesn't have a good foothold. But, since you are limiting contributions only to individuals in a constituency, then how will the party's candidates in a new state effectively raise money? If you say the party could help them, then aren't you creating a loophole: namely, non-constituents from other states could give money to the 'party' which in turn would be channeled to the candidate?