Steve Sailer's been asking about the feasibility of Hillary stepping down. Around 20 states have already finalized their ballots so such an action would require an enormous amount of rule-breaking. That's her forte so maybe it's a viable option anyway.
What seems more 'problematic' from Team Clinton's perspective is the assumption everyone considering Hillary stepping down seems to be making, that Tim Kaine would naturally take her spot at the top of the ticket.
Many Bernie supporters were, to put it mildly, dissatisfied with the nomination process but will end up voting for Hillary anyway. After all, the birdman himself is committed to doing so, so they can hold their noses and do the same.
But by falling in line when he represented a minimum of 45% of primary and caucus voters--quite possibly more given the DNC rigging--how would those reluctant Hillary-voting Bernie supporters take their man being passed over again and the nomination being given to Kaine if Hillary drops out? Had Kaine competed in the primaries, he would've been neck-and-neck with Martin O'Malley, Jim Webb, and Lincoln Chafee at 1%-2% of the vote. He's a non-entity.
Giving the nomination to Elizabeth Warren would be even more conspicuously undemocratic. While she's more popular among Bernie supporters than Kaine is, she's not Bernie, she didn't run for the presidency, and she wasn't even picked for the VP spot by the person who won the nomination.
Tangentially, "basket of deplorables" is a staggeringly stupid phrase for Hillary to have employed. "Basket" is a word that brings an old maid at a retirement home to mind, right as it's becoming difficult for Hillary to speak or walk without assistance. "Deplorables" isn't a noun (until now--and Hillary owns the credit for it becoming one, to the unending delight of her opposition everywhere). By superciliously dismissing the concerns of a roughly a quarter of the electorate, the contrast with Trump's "I am your voice" couldn't be any starker.