Last night, 68 percent of Iowa's Democrats did not vote for Hillary Clinton. The characterization of Hillary as the inevitable nominee now appears obviously foolish (or at least a little premature).
Barack Obama scored significant momentum with his win, and still-deciding voters looking for an "anything but" alternative to Clinton might ditch Edwards as an option.
Even if some potential voters previously only saw Obama as a favorable second choice to Edwards, they might ultimately bolster Obama and avoid splitting the anti-Hillary vote between the two, risking a Clinton victory. Among her own party, a candidate's likelihood of beating the polarizing Clinton may be just the ticket.