If Vilsack wins Iowa and Hillary Clinton comes in second, it will help her, but only be what people expect.
If Clark, or Edwards, or whoever, comes in a strong third, they benefit most of all.
If anyone beats Clinton for second place in Iowa, and it could certainly happen, then that person is in position of strength, and she darn well better come in first in New Hampshire.
Gore is an exception to this. He would have beat or tie Hillary in at least one of those first two states or he would also not have met expectations.
Iowa also remains important because the last place finisher, depending on the results, will get pressure to drop out.