I don't care much for Trump. He is a bloviating ball of ego.
But the Democrats shouldn't be screaming about treason or the view that Trump asked the Russians to commit espionage.
When the DNC's emails were disclosed by Wikileaks, Clinton's camp was quick to ascribe the access to, and disclosure of, the DNC emails to the Russians. Even if Clinton's camp (Mook) did not have evidence to substantiate this large opinion, anyone reasonable would agree that Mook's assertion was both fairly rational and likely. Perhaps of interest is the corollary question of whether another foreign government (in addition to Russia) obtained access as well.
So it is hardly a stretch for Trump to assume that the Russians and other foreign entities already have access to the Clinton server emails, and indeed, almost every foreign security expert believes this to be the case (again, formidable direct evidence appears wanting). Whatever Trump's flaws are, and they are legion and give rise to a ton of doubts as to whether he could ever lead, he does not hesitate (unlike like establishment Republicans) to get into a street fight, and doesn't care about acting Presidential. He is not all that attentive to the truth, either, but since he speaks so bluntly to the establishment (both Republican and Democrat), he gets away with it under the guise of being a refreshing character and frankly will continue to do so. I am accordingly perplexed as to why Democrats are giving so much attention to him by screaming "treason". One, it will give rise to the belief that the emails, which supposedly no longer exist and were only ever about personal, non-governmental information, did in fact exist and were absolutely about government operations. Democrats may argue differently, but certainly it makes no sense to scream treason and national security risks over emails which describe Clinton's yoga habits. Two, it gives rise to the optics that the emails had national security implications, despite Clinton's long protestations to the contrary. Three, she has to move past the email controversy to win (and the media is inclined to help her do it), but reacting to Trump's street fighting on the topic is surely not a way to do it. Fourth, he even has a legal defense to his statement - a treaty signed between the US and Russian in the late 90's obligates Russia to notify the US when it becomes aware of a violation of US laws (something Russia did do with the Tsarnaev brothers, by the way). A trial lawyer could not have dreamed up of a worse response to Trump's bloviation than screaming treason - giving such attention to him is just a mistake. One would hope that the Clinton campaign will learn, and learn quickly.
There are massive numbers of elitist Republicans who grossly, and I mean grossly, underestimated Trump's appeal in the current political environment. They are for the most part elitists, fooled by the fact that they believe they are smarter or better educated or with better breeding than others (a trait they share with elitist Democrats, who merely possess a different view of their own moral superiority), Democrats should not commit the same errors in the next three months. To wit, there are a whole lot of people at the Democratic convention with signs which reflect absolute hatred of the TPP. Look, most economists, and indeed, wonky types (Obama, Clinton) will with good reason argue for the kind of global cooperation and trade envisioned by the TPP. Heck, I have a hefty economics and legal background and "get it", too. But lots of rank and file people, many of them in the Democratic crowd but also those inclined to vote Republican, are all too ready to believe that their fall, or potential fall, from the middle class is due to poorly constructed global trade deals, with relentless pressure on the bottom and from rising costs from a swell of undocumented people. Don't bet on Trump quitting beating this drum - in fact, he is only getting started, and it is easy for him, as he thinks getting a good trade deal is scarcely different than cutting a good development deal on a resort in the Bahamas. It doesn't take genius to figure out what has been resonating for Trump (immigration as mentioned above is one other such subject), and he won't quit at it. I recall Sebastian Coe stating that success comes about by finding a balance between confidence and humility. Democrats need more of the latter to beat this guy, and would be well advised to quit calling Trump supporters stupid, and convey the notion that they are thoughtful problem solvers for the middle class, and be disciplined in their dealings with Trump.