Running negative. No one has ever run such a negative campaign as the one Hillary ran against Donald Trump. She started them well before the official launch of the national campaign, before either of them was officially the candidate. There were numerous cuts but they were all the same message, repeating things that Trump had said over years or decades. This was the worst thing that Hillary could have done. After months of hearing the same Trump quotes, they no longer shocked. They just faded into the background. Hillary inoculated the voters against Trump. The few positive ads that she ran failed to tell voters what she would do for them. That gave Trump space to tell voters what he would do for them.
Expecting to rebuild the Obama coalition. Hillary expected that, as Obama's chosen successor, his voters would automatically default to her. But Obama was a fresh face and an outsider. Hillary became First Lady before many voters were born. Democrats voted for her out of duty but it was a joyless campaign.
Lies and prevarications. Hillary has the reputation for never telling the truth when she can lie or tell a half truth. She did both constantly and, when she did tell the truth, she did it in a lawyerly way. She flat out lied when she said that her personal email server was because she can't use two devices at a time. She was forced to make admissions but never came out and told the entire truth. She hid the fact that she had pneumonia until she collapsed in public and even then spent hours insisting that it was just dehydration.
Wall Street and the Clinton Foundation. The voters were still mad at Wall Street about the Great recession. Both Sanders and Trump harnessed this anger. But Hillary was a creature of Wall Street. She made millions giving speeches to big banks. So did her husband, Bill. The Clintons' speaking fees were high, too. So, were these institutions simply paying for big-name speakers to impress the attendees at their functions or were they buying future good will from the next president? Again, we don't know. Hillary danced around the issue a lot and insisted that she'd warned the banks to be more careful with their investments but the one leaked transcript show just the opposite. She spent her time congratulating the banks on their wisdom. People wanted an outsider and she was the ultimate insider. She was even warned that accepting speaking fees from banks would hurt her and she brushed the warning off.
Libya. If it wasn't for Hillary we'd never have overthrown Libya. This was a disaster for the Libyans and it lead to the death of an US ambassador. It also poisoned the US's relationship with Putin. Libya's Qaddafi had been cooperating with the US including voluntarily dismantling its nuclear program and we overthrew Qaddafi anyway. Putin was convinced that he'd be next and blamed Hillary. Personally, I don't think that the release of emails hacked by the Russians had much effect on the election but if it did, it can be traced back to this.
The Email Server. The FBI couldn't have announced that they had reopened an investigation of misuse of classified information if Hillary hadn't used a private server in the first place. She wanted to have total control over what got out. She even went so far as to delete more than half of the emails on the server. Why did she do this? Excess concern for privacy? To hide influence peddling? We'll never know but the speculation darkens an already tarnished reputation (more on this later). In addition to this, she was careless with classified material. It just came out that she regularly forwarded emails to her assistant, Huma, to print and she forwarded them to her husband, Anthony Weiner. If this had made the headlines before the election she might not have lost the popular vote as well as the Electoral College.
In one of her first public interviews, Hillary Clinton admitted to making mistakes but was vague about them, preferring to focus instead on factors outside her control.I disagree with her assessment that intervening events were the cause of her loss. She made lots and lots of mistakes and some of them led directly to the intervening events she complained about. Here's a partial list of mistakes:
So, did we make mistakes? Of course we did. Did I make mistakes? Oh my gosh, yes. … But the reason why I believe we lost were the intervening events in the last ten days. And I think you can see, I was leading in the early vote. I had a very strong — and not just our polling and data analysis, but a very strong assessment going on across the country about where I was, in terms of the necessary — both votes and electoral votes.
The Basket of Deplorables. You just don't insult somewhere between 1/4 and 1/2 of the voters. Ever.
At one point Hillary released an internal video were she asked why she wasn't ahead by 50 points. Given all of her mistakes, it's a wonder that she was ever ahead.