Even assuming Clinton manages to defeat Trump, Bernie Sanders probably lost democrats a couple Senate seats this year. Bernie Sanders probably lost democrats ten house seats these years.
Oh, I would love to hear the tortured logic underlying this statement. Next, you can tell me how Sanders is also responsible for the thinning of the ozone layer, male-pattern baldness, and the cancellation of Firefly.
Down ticket races suffer a drag from the top of the ticket. Every time Clinton's numbers go down, so do Senate Democratic candidates. We dont have as much data on house races but it seems reasonable to suppose the same happens.
It's not logic. It's empirical observation.
I.e. "I feel like blaming Sanders for something, so I'm going to throw out an extremely weak causal chain and pull some numbers out of my ass".
You're positing the following:
A) Clinton's weak numbers are due to the efforts of one Sen. Bernard Sanders, rather than any of her own weaknesses (because we all know Her Divine Radiance (PBUH) *has* no weaknesses).
B) Clinton's polling dips directly impact down-ballot races to a measurable degree which is equal or larger than other factors intrinsic to each race.
But you have no evidence to indicate either is true, and certainly not to the degree that you can measure it and come up with a number of races that can be blamed on Sanders.
On point A: Sanders has been nothing but a cheerleader for Hillary since the convention. Bernie didn't give her pneumonia (OR DID HE?? DUH DUH DUHHHHH!) and he certainly didn't botch the handling of the PR around it. Bernie didn't parse her words for her regarding her email server, in fact he declined to attack her on it during the primary. At this point, the statute of limitations has run out on blaming any new polling dips on Bernie. And as was pointed out, she's been unpopular with a lot of people for a long time now. Many probably like myself, who had no problem with her as Sec. of State, but as soon as she resigned and the rumors began swirling of a Presidential run, were like "Oh fuck plz no no no", because it didn't take a mystic to foresee the metric ton of baggage she would bring into the race, deserved or not.
On point B: Down-ballot pressure is a thing, but it's not easy to quantify. And in this cycle, I'd say Trump is exhibiting more downballot pressure than Clinton is. Look here in NC -- you have a two-term incumbent GOP Senator with no real scandals or glaring weaknesses, who was so expected to win in a cakewalk that the Dems didn't even field a major candidate -- having previously thrown Erskine Bowles and Sec. of State Elaine Marshall at him, and now Deborah Ross is averaging a point ahead of Burr, despite most people not knowing a damn thing about her.
If I were to rank the factors affecting this race, I'd say (from weakest to strongest) it's:
1. Hillary Clinton as Democratic nominee
2. Burr's lack of...anything in 12 years to point to as a major accomplishment.
3. Trump as GOP nominee
4. The fact that the GOP governor and GOP legislature are about as popular as a canker sore right now with all but the diehard bigot wing of the Republican Party.
As they say, "all politics is local". And in this race, local/state effects are trumping (pun intended) the national race. Even progs and indies who might still be sore about Sanders or generally distrustful of Hillary Clinton (PBUH) aren't going to suddenly vote for Burr, because they're unconnected.
I could potentially see an effect in Debbie Wasserman-Schultz's race. If she loses that, could be worth looking at exit polls to see if the whole DNC-Sanders dustup was a factor in voters' decisions (and I assume pollsters will explicitly ask that). Outside of that one House race, you're gonna have to do better than "I feel like this should be true, so it's true".
I'll even help you -- Harry Enten over at 538 has a regresson analysis that argues
there is a correlation on Senate races. Although I think he's overstating the effect, and the slope is not 1:1, nor is correlation causation. Easy enough to say "Hillary and the Dem senator are both doing badly in Idaho, because
it's fucking Idaho."
House races are probably far more insulated from down-ballot effects thanks to gerrymandering.
In the vast majority of those races, the party of the winning candidate is all but decided before anyone even files to run. Ballotpedia predicts that only 24 of the 435 House races (5.7 percent) will be truly competitive in the general election.
I think it's beyond a stretch to say that Sanders is going to cost the Democrats 40% of the available seats up for play.