Just an anecdote
This evening I was at a meeting of a subcommittee of the local DFL Senate District Central Committee. The purpose was to go over what needs to be done for the local precinct caucuses and the senate district convention that follows the caucuses. This wasn't a Bernie group (though most the people there are Bernie supporters), just a bunch of party hacks making sure we once again get things arranged so we appear to somewhat organized on caucus night.
We were in the back room of a local restaurant and one of the guys who works there (I think he may have been the night manager) wandered into our room and asked if this was the DFL group. Once assured we were, he announced that he wanted to know what he needed to do to caucus. I'd guess he was somewhere between 25 and 30 and he said he had never been to a caucus before.
"What made you decide to attend this year?" We all asked.
Turns out he really likes Bernie and he keeps hearing if he wants to help make Bernie president the caucus is the place to be. So we were able to give him instruction on how to find out where he should go on March 1 (he already knew the date - that alone warmed our hearts).
And this is why, as we made our plans, we assumed we will have a large turnout this year of many newcomers like this guy and we're not so sure the other campaigns see them coming.