I have no idea how the real election will go, but I think these polls where you pit a known person against an abstraction are pretty useless. Those polled seem to view the abstraction as an ideal candidate or the one among many choices whom they might vote for (think of the disparity of those thinking of Ron Paul, Pawlenty, Gingrich or Palin).
Further, the campaign will change everything. We have no idea what useless, trivial or false issues will be raised to sway the electorate.