With everything he has said and done, how is it possible to focus on only a few key things to attack him on.

"Our problem is a target-rich environment" said one Clinton ally, noting that nearly every day there is a news cycle with damaging headlines about Trump.

Aside from a target rich environment, Trump has been so unpredictable that it's hard to use any one thing and turn it into a narrative strong enough to actually impact voter opinions.

"Right now, they're doing a little bit of everything to see what works. You can spend all day, every day, going after a hundred different things, and those things can add up to less than one hundred. They may not weave into a narrative, or you may not be able to drive any one of them home for long enough. You need discipline." said Dan Pfeiffer, a former senior adviser to President Obama.

As Clinton struggles to define Trump, her campaign has taken the approach of throwing things against the wall and seeing what sticks. As Politico reports, first on the list of things to try is the talking point that a Trump presidency would be terrible for women.

"What's really clear," Neera Tanden, Clinton's former top policy adviser, said on a conference call with reporters, "is Donald Trump has made it entirely clear throughout the entirety of his campaign that he would be a terrible choice for women voters."

The next trial balloon would be to try and play up that Trump would be bad for Latinos and middle-class Americans.