The inimitable Dick Morris has an answer to that question and Hillary won't like it; she is basically an unattractive candidate:

In the abstract, Hillary is a captivating idea. The first woman to run for president, she is the living reminder of the better economic times and international peace of the Clinton administration. But, up close and personal, she is far less attractive. As the rest of the country is exposed to the former first lady, if they emulate the voters in Iowa and New Hampshire and revise their opinion of her, the results will not please the Clinton camp.

The conclusion is obvious: neither Hillary nor her staff know how to campaign. After the Clinton re-election in 1996, they have never been tested in a competitive race. When Giuliani dropped out of the New York State Senate race and the young Congressman Rick Lazio had to enter at the last minute to try to stop Hillary’s bid, the conclusion was pre-ordained. Hillary’s re-election was a cakewalk against a totally under funded opponent. She doesn’t know how to win.

Hillary’s experience has been limited to the insider back biting of Washington where she is an expert at using her secret police — a small army of private detectives — to unearth negatives about her or Bill’s opponents. (Even former U.N. Ambassador Andrew Young recently admitted that Hillary ran the effort to discredit women who might come forward and accuse Clinton of misconduct.) But, when it comes to campaigning, advertising and winning an election, these folks and this candidate don’t have a clue.