Dr. Kent Bottles,who heads the Institute for Clinical Systems Improvement, blogs about this question.
He concludes by quoting Sharon Begley in a Newsweek column:
"Anyone who believed that the battle over health care reform would be waged on facts, logic, reason and concern for the less fortunate...probably also scoffed at Lyndon Johnson's daisy ad. As politicians and strategists (at least the successful ones) have finally learned, appeals to emotion leave appeals to logic in the dust. And no emotion moves people more powerfully than fear."