I voted "totally disagree" for the reasons
@FreeBaGeL and
@Maurile Tremblay are saying, but will try to articulate my thoughts.
The people in the "middle" are presumably independent and vote for either side. It's a major assumption to assume they are even voting, and if they do, it is unpredictable they will vote for your preferred side of the aisle. Why put energy into trying to persuade unpredictable people?
If I were a political strategist for either side I would want a charismatic candidate above all else. Someone who inspires their base to get out and vote. Think of the last handful of presidents: Reagan, GHWB, Clinton, GWB, Obama, and now Trump. The only two that I view as lacking charisma are the two Bushes, but W had more. GHWB ran against Dukakis, who was utterly devoid of charisma, and is the only one-term president in the group, losing to Clinton. The two Dems that ran against GWB (Gore and Kerry) could suck the charisma out of the room.
I'm not going to argue that it's ideal, since this can lead to a charismatic figure like Trump getting elected, but inspiring people to get out and vote is the most important thing. The fact that people who were attracted to Bernie Sanders last election switched over to vote for Trump tells me that charisma matters more than policy. I try not to vote entirely based on this, but I do admit Obama really inspired me in 2008.
The worst candidates the Dems could run this election are Biden, Warren and Klobuchar