Gnu, there is an old saying (incorrectly, I think, attributed to a fairly recent politician) that "all politics is local". This is the reason that we can have Democrats that are further right than some Republicans and Republicans that are further left than some Democrats...because they reflect the positions of their constituents and because the alternatives those voters had did not. That is, if a fairly conservative region has the choice between a fairly conservative Democrat and a very conservative Republican, they vote Democratic. On the other hand, a Republican with identical views as that conservative Democrat would go down to resounding defeat if he were running in a much more progressive district. The Republican party does better at keeping their senators and congressmen in line, IMHO, because (other than a couple of outliers in upper New England) they are all in the range from center-right to far right. Democrats, on the other hand, cover the spectrum from center-right to far left.