"A candidate's unfavorability scores almost always climb during campaigns. If the pattern holds, Clinton has a historically high hurdle to overcome," Fournier reported last week.

But more is at stake here than just the presidential race, Democrats said. A weak nominee at the top of the ticket can threaten the party's candidates further down the ballot.

Earlier this year, Markos Moulitsas, whose fiery liberal political blog, Daily Kos, is widely read by Democratic Party activists, said Democrats were increasingly concerned about whether Clinton would hurt the party's other candidates in competitive congressional battleground races if she led the party's ticket.

"Hillary would be a drag on races lower on the ballot. In fact, her potential nomination is already creating all sorts of headaches for Senate and House recruitment efforts in tough states and districts," he wrote.

"This is a dynamic not at play with any of the other serious candidates," he said.

Writing in the National Journal late last month, reporter Marc Ambinder said, "Some Democrats fret about state legislators in marginal districts" if Hillary is the nominee. "And several freshman members of Congress have told their political consultants they're not quite sure what impact Clinton will have."

Another huge manifestation of her weakness as a candidate is in the head-to-head matchups with Republican front-runners. She runs behind or about even with former New York Mayor Rudy Giuliani in a wartime climate that is supposed to be favorable to Democrats.

Helping Giuliani to overcome a negative environment for Republicans is a favorability rating of 55 percent and a low unfavorable score of 32 percent, according to a Gallup Poll released Aug. 10.

These numbers suggest that Democrats are not running away with this election, that their front-runner still has huge political obstacles to overcome and that Democrats have a lot of soul-searching to do before they choose who will lead them in next year's election.