Maybe Sanders is the "front-runner," at least according to polls of voters in Iowa and New Hampshire. Then again, I'm old enough to remember GHWBush coming out of New Hampshire in 1979 with the "Big Mo." The only reason he got into the non-visitors section of the White House for the next 8 years was because he was Reagan's VP.
And who has ever won New Hampshire, or Iowa's straw poll, and gone on to sweep all before them, especially in a very crowded field? Quick history question: was Trump the front runner in the GOP primaries a year before they were even held?
Throwing out this kind of conspiracy crap is not a sign of seeking unity in the party. Like Trump, it's the act of someone who feels entitled to the victory and the office. You may say that's Sanders' supporters, not the candidate; but who seriously separates the most ardent supporters from the candidate whose message draws them? Like Trump, Sanders depends on his "base" to get anywhere at all.
As Yeats said: how can we know the dancer from the dance? As Molly Ivins observed about the rules of the Texas Legislature: "You gotta dance with them what brung ya."
Same as it ever was.