Cox and Forkum handle the Dem's concerns that Hillary Clinton as Presidential Candidate would have a negative impact at the bottom of the party. They usually have some good quotes and commentary, but I usually just go there for the illustration.
To quote, though, a little tidbit:
A strategist with close ties to leaders in Congress said Democratic Senate candidates in competitive races would be strongly urged to distance themselves from Clinton.
"The argument with Hillary right now in some of these red states is she's so damn unpopular," said Andy Arnold, chairman of the Greenville, S.C., Democratic Party. "I think Hillary is someone who could drive folks on the other side out to vote who otherwise wouldn't."
Golly, but politics sure are fun.