Earlier this year, somebody got into the DNC systems and did a data-dump onto Wikileaks. The leaks were mildly embarrassing but not crippling; it showed that the DNC was in the take for Hillary and the party chairwoman was forced out amidst Sanders camp outrage. In addition, some unflattering comments at various demographic groups that played into smug secular liberal stereotypes were revealed.
Neither were surprising. The pro-Clinton bias and the liberal smugness were largely understood, and the Wikileaks data-dump merely confirmed that. However, the Democrats got some mileage out of it, because somebody (likely the Russians) had it in for Clinton, and we can't let that happen to our great democracy.
The Democrats look bad due to some sunlight disinfecting their contempt of swing voters and pro-Clinton bias, and Trump looks bad because (as the meme goes) his pal Pooty-poot had his hackers do dirty deeds dirt cheap.
[Update 4:45PM-Here's an interesting set of plausible three-carom shots by the KGB's descendants-
It is always possible that Russian intelligence was not sophisticated enough to recognize that what they had was not decisive. There is also the possibility that they wanted to create a damaged presidency. The goal was not so much to break Clinton as to make sure that if Trump won, a shadow would hang over him. In this truly twisted theory, the hack occurred to give Obama the opportunity to launch an investigation that might tarnish Trump. This is a long shot, but given the facts it is as plausible and implausible as the idea that Putin loved Trump and wanted to help him.
There is another theory. The Russians did hack the files but their primary purpose was to create chaos in the United States. In this theory, the Russians are ultra-sophisticated and know that by hacking the files, they could sit back and let the Americans eat their young, as they are bound to do. They had no strategy in mind beyond destabilization.
Did that make the difference in places like Michigan and Pennsylvania? Maybe. But who's to say that the Putin-hearts-Trump meme didn't make the difference in Nevada and New Hampshire?
Despite CIA leaks pointing the finger at Russia, we don't have firm evidence of whodunit. Hackers can route things through your laptop, Evil Stevie's thermostat and an Elbonian cell-phone en route to its target; any Russian prints on it could be real or a false-flag operation from elsewhere.
We had a squeaker of an election; with four states being within a percent, three of which went to Trump. It was going to be a squeaker with or without the DNC-Wikileaks episode. Any number of things contributed into that witches' brew, from Comey clearing, then unclearing, Clinton over Servergate to the Clinton team neglecting an old-school, yard signs and door-to-door canvasing ground game in Rust Belt states to our friends at Wikileaks.
Getting to the bottom of the DNC leaks is a good idea. Holding the Electoral College hostage over it, as Politico seems to want to do, seems to be overkill. If Republican electors want to abandon Trump, they have that prerogative. They have multiple reasons beyond whether Kremlin-sponsored-gremlins were behind the most recent Wikileaks episode. If there were firm evidence of that, we'd likely have seen that come out sooner.