Politco:Email woes, Sanders surge rattle Clinton's Hill backers

“She’s struggling. And you can see the numbers are moving in a direction she wants to change,” said Durbin, who spent Labor Day alongside Clinton. Of Democratic primary voters drawn to Sanders, Durbin added: “It isn’t like they’re dead set against Hillary. But they find Bernie’s message to be the right message.”

“Bernie has kind of gone off like a flare. How long that lasts remains to be seen. I don’t think he’s doing the party any damage, so I don’t mind it,” said Sen. Sheldon Whitehouse (D-R.I.). “She’s been trying to keep a low profile and let the Republican candidates try to alienate everyone they can possibly … alienate. So it’s hard, in that strategic mode, to compete with Bernie.”

“I believe she’s going to be at her best if she does get behind,” said Missouri Democratic Sen. Claire McCaskill, one of Clinton’s most vocal supporters on the Hill and one of the few Democratic lawmakers to publicly question Sanders’ electability. “If she does get behind, it will finally get through to the American people that she’s a fighter and that she wants to earn this and that she doesn’t believe it should be given to anybody.”

“How’s the campaign going? I don’t know. Just what I hear on television. I want to talk to her,” Manchin said. “We’ve always had a good relationship. We need to sit down and talk it through. I’ve got concerns with the climate [plan].”

Though Clinton isn’t electrifying Iowa in September, Democrats believe this tough stretch will be a faded memory once actual votes are being counted. But, they admit, it’s going to be a long four months until then.