There is a finite number of votes cast. There is also a finite number of potential votes. Most people who could vote do not. You are correct in that many people choose not to vote.There are a lot more non votes than votes and with those, the Dems could make the same argument.
For about all of my life I did not understand why so many did not vote. I have never missed an election at any level. Even in a small town election where I had lived only a short time and did not know the candidates or the issues well enough to believe I could make a good decision I went to the poll and got my ballot and just blanked it out.
After all these years I am beginning to understand why at least some people choose not to vote. I don't know what I'll do...probably vote....but there is no way I'll vote for somebody just because he's got the (R) or against somebody just because he's got the (D).
You are going on and on about health care---fine, I agree it's a big problem. But it is no more a big deal than taxes, or abortion, or national security (much less so IMHO). Therefore, it makes a HUGE difference if I vote for someone with an (R) next to his name because regardless of health care, I know that that person will put Frist instead of Daschle in; and that in turn shapes everything else.
So prescrip. drugs become a reality. That in no way changes what the DEMS do on national security (dangerous), abortion (murderous), or taxes (larcenous). So again, not to vote it to choose Dem.