I found the following compelling.

From Telegraph:

Perhaps the fatal flaw of Mrs Clinton’s campaign is her husband. On the campaign trail, Bill Clinton is adored by Democrats but talks endlessly about himself. Her implicit claim to be striking a blow for feminism is undermined by his presence, which reminds people that without him she would be nothing.

And while Bill’s 1992 campaign was about a new generation taking over Washington, his wife’s seems – to modify his slogan of 15 years ago – to be about building a bridge back to the 20th century.

Tensions between the Bill and Hillary camps are heightening as the going gets tougher. Privately, her aides fret about the potential for fresh revelations of her husband’s infidelity. And Bill’s easy rapport with voters provides a ready contrast with Hillary’s awkwardness, reminding Americans that if he has an heir in his ability to connect to crowds on campaign trail, it is not his wife, but her would-be nemesis.

By the way, this echoes something I’ve said earlier.

Politics Is Hillary's Fatal Flaw…Bill?