The main theme of Crooked Hillary's campaign is that she's not just any corrupt Establishment next-in-line candidate -- she's the first one to also be a woman. In their lazy insulated minds, that would make her male opponent an enemy of women.
Even during the Democrats' own primary, voters showed little interest in this approach, either the "first woman" part or the part about "my enemy is a woman-hater for getting in this woman's way". During the general election, non-Democrats including independents will show even less patience for it.
Trotting out Pocahontas Warren was an even worse mistake, since doubling down on a tiresome and soon to be annoying tone will further alienate general voters. Also, it immediately deflates the tepid enthusiasm for Hillary being the "first woman" -- now that she's paired with Pocahontas, are they a first pair of women, or maybe part of a first larger movement of women? The "first woman" candidate would only stand out in stark contrast if those surrounding her were men.
The emphasis is no longer on Hillary being "first," which suggests reaching a historical milestone of fairness (for what that's worth), but rather on a broader "women vs. men" confrontation that has nothing to do with fairness but inter-group warfare. And the battle of the sexes is as old as mankind, therefore not a historical milestone, as originally billed just a few days earlier.
"Oh great, yet another brigade of nagging scolds is teaming up in the political arena -- get ready for Prohibition part 2."
The Trump movement can only rejoice at Team Hillary stepping on its own dick twice in the first week of its general campaign -- her status as "first" was immediately overshadowed by Pocahontas becoming a de facto "second," and then the "fairness milestone" thing quickly devolved into a "hostile battle of the sexes" thing.
Once Trump starts to really unload on her during his Monday speech, they're going to find out that this Republican candidate isn't the wuss that low-energy Jeb Bush would have been, sitting there and taking their "war on women" bullshit the entire time.