Has Sanders ever helped downticket Democrats?
He's supported only three--who happened to endorse him. Which, contrary to the article cited by Dpareja, actually
is unprecedented. Never has a politician run supporting--only--those lower tickets that endorsed him (him because ever president ever was male).
But going to dpareja, nobody for a minute ever denied that the bulk of the cash for the HVF goes to Hillary... with second dibs on the remaining money going to the DNC* and third dibs to state parties. In fact, snopes reported as much--it's how the donations are set up and operated. But, "less than 1%" of "61 million" still comes out to $610,000 for the down ticket ballots (give or take), which is more than would otherwise be raised.
*Most of this money to the DNC would then be redistributed to the most competitive state competitions. But just ignore that fact because it's inconvenient.