You should take a look at my most recent post:
If you want a progressive President, elect Elizabeth Warren
What the data tell us about the potential Democratic Presidential candidates
Regarding your question as to the last time the DNC discussed Universal Health Care, that is not their role. I do think most members of the DNC likely favor a single-payer system, as Democratic activists tend to be more liberal than the average voter. But as I described in my post, the DNC discusses process, not policy.