First, I think some people are being too harsh on Clinton’s loss. She did pull out an overall popular vote victory. The problem was that a lot of people thought her campaign would be a slam dunk and so they see a fairly close loss as a major failure. I never thought that, I always assumed, given her weaknesses as a candidate, it was going to be a very close thing so all credit to her for achieving what she did.
That said, I think I finally figured out what her biggest problem was. Every single election boils down to one major issue: Do you want More of the Same or Something Different? Dress it up however you want, every candidate in every election is promising either a continuation of current policies or a change in policies More of the Same or Something Different.
Clinton’s biggest mistake was running a de facto Something Different campaign. I get that running after a two term incumbent in the same party is tricky which is why it often doesn’t work (Nixon after Eisenhower, Gore after Clinton). But the central idea of Clinton’s campaign should have been building on the success of Obama’s administration. For whatever reason she seemed to still be running against W.
That single mistake, led to other mistakes. Once she began running as a Something Different candidate she also decided to run on the left rather than in the center (or right) either of which would have probably been more successful. This led to lots of tone deaf moments as she had to present the idea that women and minorities are in a uniquely terrible position at present under the Obama administration.
This led to a terrible echo chamber effect (the biggest problem of the left in the US) where she did dumb things like enlist Lena “I’m a big pile of pudding” Dunham to let her say all manner of foolish things in Clinton’s name. I can’t imagine Dunham winning a single vote for Clinton and I imagine she repelled some that might have been on the fence and inclined to vote for her.
The eternal problem of the left in the US is the eternal temptation to fall into the old ¿Quién es más progresivo?* trap. Clinton fell into it and wasn’t the only or main reason she lost but it certainly didn’t help.
*popculture reference to an old Saturday Night Live skit with Bill Murray, ¿Quién es más macho?