Being rather simple-minded, I tend to view politics much in the same way I do the Great Sport of boxing. Recently, we've had difficulty in securing any bouts for my son. (In fact, we have a problem getting him sparring.) We looked into the Golden Gloves this year: usually, our state has been divided into four districts; each would hold a tournament, and then the final four would compete for the state-wide title. There are two classes in each weight division -- novice and open -- and the winner of the open class moves on to the nationals.
This year, due to decreasing numbers, there was only one, state-wide tournament. And there was no one else my boy's weight in the novice class. So we looked at open class; again, no one.
We could have entered him in one or both, and he'd have "won" the title(s). If I put him in open class competition, he'd be on his way to the nationals, as we speak. But he doesn't yet have that level of experience.
I think that the progressive wing of the Democratic Party is in a similar position. We need to get more experience in running candidates on the local, then state level, before we are in a good position to have our type of candidate try to win the presidency. That's why in 2016, I'll be investing a heck of a lot more effort on the other elections, than the presidential race.