Efforts to make Hillary Clinton more appealing to voters isn't apparently working, based on recent poll numbers — and it's frustrating her campaign."I don't know if I have an answer to that," Democratic strategist Jim Manley toldwhen asked what more could be done to soften the Democratic front-runner's image. "This cake has been somewhat baked by this point in time.""This is frustrating to me," he added. "But I'm afraid there is no silver bullet out there. I spent lot of time with her over the years, literally hundreds of hours with her. It's difficult to reconcile."She is a warm, generous person — but for whatever reason a lot of folks aren't buying it."Manley worked as a spokesman for Nevada Democratic Sen. Harry Reid when he was majority leader.Just days before the California primary on Tuesday — one of five state contests on the last day of the 2016 season — Clinton's favorable numbers remain low, and she continues a fierce battle against Bernie Sanders in the Golden State.Fifty-three percent of Americans viewed her unfavorably in a recent, compared with only 44 percent who viewed her favorably.In addition, afound late last month that nearly two-thirds of registered voters considered Clinton untrustworthy and dishonest.The former secretary of state's campaign aides acknowledged that the email scandal, boosted by last month's damaging report on her private server use by the State Department's inspector general, has dampened her image, the associates said."Has it brought her down in the polls?" one friend asked the Hill. "Of course it has."The Sanders battle — and now, the specter of facing Republican Donald Trump in November — are also taking their toll, they said.But some Democrats said that Clinton can recover, especially amid Trump's own unfavorable ratings."I really do think she needs to shake it up," one campaign surrogate told the Hill.