Bernie Sanders has officially endorsed Hillary Clinton. That having happened, there are only a few things to say.
Any closely contested primary -- as this one was -- is going to have moments of bitterness and animosity. There were certainly times, towards the end, where I thought Sen. Sanders was veering too far into grudge territory. But both his conduct and my assessment of his conduct were made in the heat of the moment. Now that we're out the other side, I'll say again that -- my support for Clinton notiwithstanding -- I think Sen. Sanders made the Democratic Party stronger by running. I think he effectively leveraged his considerable successes to bring about genuine and positive changes in the Democratic Party platform -- the most progressive in the Party's history. By mobilizing the left flank of the Party, he'll help ensure that Hillary Clinton is a more effective and more progressive president than she otherwise would be -- not because she yearns to be a neoconservative hack, but because politicians respond to organized pressure and too frequently the left shuns political organization.
I also suspect that the vast majority of Sanders voters will come home to Clinton -- as they should: The gap between him and Hillary Clinton is minuscule compared to the chasm between either of them and Donald Trump. Of course there are some dead-enders who are making a lot of noise right now -- that, too, is typical in a closely-contested and bitter primary (remember PUMAs?). But they're a distinct minority that misconstrues the key lesson of the Sanders campaign. Sen. Sanders shows that if you push inside the system -- he ran as a Democratic, not a quixotic independent vanity run -- you can bring about genuine progressive reforms. If your purity is too precious to even fathom compromising with 85% of your side of the political spectrum (let alone the country), you usually end up with nothing.
So as far as I'm concerned, any bad feelings or ill will is water under the bridge. Senator Sanders ran a good, strong campaign that accomplished many things he can be proud of. Focus on that, and focus on bringing about the electoral outcome come November that will best turn those political accomplishments into genuine policy reforms.