Karen Tumulty of Time has an online article that quotes a senior Democratic strategist close to the Clinton campaign. I think the strategist hits the nail on the head. It's what I've been thinking for some time (emphasis mine):
But it's possible that the most difficult problem is not Obama; it could be Clinton. How can she retool her message — and her identity as a virtual incumbent — to resonate with an electorate that seems to yearn more for change than any other quality? Says one longtime Democratic strategist, who is close to the Clintons: "Fundamentally, she is who she is; she can't change who she is, and maybe this is not her time."Disclosure: I support Barack Obama, and I am a volunteer for his California campaign.