Clinton's message is now so tightly scripted that her supporters can't articulate it

She is playing populist right now but she can't say anything that will alienate her biggest donors. If she wants their checks she has to do their bidding. With Sanders framing the issue of big money influence, the spotlight is on.

To try and level the playing field, Team Clinton came up with the meme that "Sanders is a one issue candidate." This is in part because they don't want to answer to all of the issues and differences Sanders has raised. They can't without sounding less populist but even the one Sanders issue that they do acknowledge, big money in politics, cuts strongly against Clinton.

They are stuck playing defense and believe that 'the best defense is a good offense.' Since her supporters can't make a coherent case for why any of us who aren't comfortable insiders should vote for Hillary, they spend their time trying to tear down Bernie. It all becomes very muddled in a hurry as Team Clinton takes two contradictory positions on almost everything. For example, they admit big money in politics is a corrupting influence but say 'everybody does it so they have to do it too.' On issue after issue, they plead guilty and then claim everyone does it. Called out on this, they are desperate to find some one time that Sanders also sold out (and how's that going btw?)

It may blunt the momentum but defense doesn't win. You need to stand for something that most people want, like shoring up Social Security. Mitt Romney lost with a similar strategy -- claiming that taxpayers want "free stuff". After all the mud slinging, we are voters not firewalls.