Let's see what Iowa has done for the race:
New Hampshire
1/5-6 1/4-5 1/4 12/18
Obama 38 39 37 28
Clinton 28 27 27 31
Edwards 18 18 19 18
National
1/7 1/6 1/5 1/4 1/3
Clinton 33 36 38 38 41
Obama 29 25 25 26 24
Edwards 20 23 20 18 17
That national lead, and what it could mean for Hillary in the Super Tuesday states, is all she has going for her now that she's pretty much headed for defeat in NH, SC, and probably Nevada as well. She loses that, and she's got nothing else on which to fall back.