Here's my recap/view on things:
This is a big deal for the Sanders campaign in that it can finally end the narrative that he can't win big states. There will be a huge cash infusion and optimism for his campaign, which means the campaign will go on and they'll fight harder. The PR will be great for future fights too, and can draw in the undecideds to his side making races tighter. People love underdogs, and underdogs with a chance.
On the other hand, its a huge wake up call for the Clinton campaign that inevitability and complacency, if that was the case, is bad. It's also a sign that pivoting to the general isn't enough - you still need to win your primary.
On the other hand, Sanders actually ended the day with more delegates lost. MS right now is projected to be 32-4 for Clinton, while Michigan is 69-61 for Sanders, meaning on the night, he lost 20 delegates. With him entering Tuesday at -197, he now sits at -217 with two more states done.
Because he won Michigan by such a tiny amount, he actually underperformed his benchmark which mean his required margin of victory in subsequent went up. 2% wins look good for PR, but the underlying math isn't as sexy.
What Happened with the Polls?
There will be a lot of post-mortem with the MI polls, which was truly historic on how off they were, but a couple important things to take note:
So credit is where credit is due: Sanders campaign pushed a lot of voters to the polls (the youth and Independents) which meant the polling demographics were off, but it also is tempered by the fact that the polls aren't automatically invalid now - they could have gotten it right too if they were correct in their demographics, and both campaigns apparently had internal polling that showed it would be a tight race.
This is particularly the case in Ohio and Florida, where polling is incredibly good because both states are considered the bellweather for the general election, given their status as THE perennial swing states.
What Makes Michigan Different?
Michigan saw a big Independent voter pool which broke heavily for Sanders. Michigan also saw that blacks and non-whites didn't break as heavily as they did in the South - although they're still heavily in Clinton's favor.
A big thing to remember though is that Independent doesn't mean non-partisan. In fact, Independents historically have been more likely to to vote along partisan lines than weak affiliated voters registered to parties. What does this all mean?
Well, Michigan in the past two decades has moved into being a mostly solid blue state. In addition, places like the UP (upper peninsula) and western/northern halves of the states have long had an Independent streak, but with MI as a whole going blue, those Independents are closer to the VT/NH/ME type of liberal Independents.
That means good things for WI (which has a mix of those kinds and Iowa liberals) for Sanders, and MN showed up for Sanders already. On the other hand, looking at future states, there are important nuances.
Looking Ahead
Super Tuesday 2 looms, and with NC, OH, IL, FL, and MO looming, that's 691 pledged delegates on the table, and it brings the race to half way.
Now, Florida has shown a consistent lead for Clinton. Florida has the same lack of contested primary that Michigan has had, and so its last contested primary was back in 1992, which may give you pause given Michigan was off as much as it was, but as I wrote above, Florida is on of the most heavily polled states - unlike Michigan.
In addition, demographics in Florida favor Clinton, with large Latino, black, and elderly populations. And demographics have been a better predictor in polling this election.
North Carolina is an interesting case. It isn't as Deep South as people like to think - there is a strong white liberal presence there, and NC isn't as black as the MS, AL, GA, etc. The polls showing Clinton +10 or so ahead are probably closer to the truth - it won't be a +20-30+ blowout like in VA or SC.
Going for Clinton is that the demographic is more conservative than Michigan, as it has gone red in all but one general election in the recent past. On the other hand, NC trends younger - especially in areas like the Research Triangle - so NC will get a big Sanders boost as well. That said, NC is still in the South, and while this will likely be Sanders best showing in the South (hard not to beat that bar at this moment), it's a tough hill for him to climb.
Missouri is an interesting state. It's not really a swing state, having not flipped in 2008 (although it was within .2% of doing so), and has a pretty solid conservative core. It also has large black populations in St. Louis and Kansas City, which makes up a big chunk of the democratic core.
Missouri is, as someone once put it aptly, a mix of the Deep South and Midwest. I think Sanders does well here simply based on the demographics of the state, but if the mix of conservative voters and Deep South black vote comes out, it will be far closer than states like KS/NE/OK where the few Democrats there are generally very liberal (and are holdouts basically from 3 states that have voted blue only once in the past 70 years)
Illinois is just proof that the Midwest isn't as homogeneous as people like to think. It borders WI, Iowa, Missouri, etc. but it also borders Indiana, one of the reddest states in the US.
Chicago is at the center of Demcorat voting in Illinois, and Illinois has a HUGE black population going for it. It also has a huge Hispanic population going for it.
Not only that, but for better or worse (often worse), Illinois is notorious for establishment politics, especially in Chicago. Illinois also doesn't have the Independent streak that parts of Michigan are known for - and for the most part, the rural vote is too small compared to how big Chicago and its suburbs are. It also hasn't had the same Rust Belt issues that Ohio and Michigan have had.
Illinois generally views Obama favorably, and with its large urban population + minority voters, the demographics favor Clinton here suggest she should win this.
Ah, the big question here is, will Michigan be replayed in Ohio? I have no doubt Ohio will be a tight race, but a couple things give me pause:
Ohio has better polling than Michigan, that can't be disputed. They've had contested primaries AND are heavily polled.
Ohio is also a swing state, with a much more conservative general populace than Michigan. This means two things:
First, Ohio has more white voters than Michigan, but more of them also vote GOP, meaning demographics for Democrat votes aren't too far off from Michigan.
Second, there are fewer Independents with a liberal streak as in Michigan, as many of them are conservatives who vote GOP instead. And Clinton has done better with the more conservative whites in the South, and large parts of Ohio align more closely with the South (near Cincinnati and Kentucky).
Both states are urbanized, although Ohio is moreso slightly (and more densely populated, with Ohio having multiple big cities), which favors Clinton in that regard.
The big question will be if the Rust Belt message translates well in Ohio. There is definitely a large white working class group in Ohio.
I expect a tight race here, but I don't expect major polling errors like MI either. The trend of a shift will be much more apparent in polling here.
Where does the Race Go From Here, and How Is it Looking Now?
The question now is, will the MI victory translate into momentum/votes for Sanders?
And if so, is it too little too late?
Next Tuesday will answer a lot of this. By that point, over half the states will have voted, and half the delegates will have been assigned.
If he loses all five, its done. The momentum story becomes a "what happened in Michigan" question, and the delegate math becomes too great.
If he loses in four and wins just MO, he's also basically done. He'll end up around -300 overall in delegates, and his favorable states afterwards don't provide enough delegates without MASSIVE wins in states very demographically favored for Clinton (and demographics have held up in this race).
Realistically, to have a chance, he has to show that momentum is real and win 2 of the big states and win one of them decisively to show he has a chance. Because here's how bad his math is right now:
Clinton can average a tie in every state with 100+ delegates, and Sanders can win everything else by an average of 20 points, and he'll still lose.
If he loses FL and IL by 10 points, and averages a tie in OH, MO, and NC, Clinton merely has to average a delegate tie in CA, NJ, and NY and he can't win without taking over 25% of every other state. And that includes Maryland - a 30% black state with wealthy whites - and DC - a 50% black electorate.
Right now, as ecstatic as I'm sure the Sanders camp is on MI, I'm also sure they would trade their MI victory for a closer defeat in TX and GA. He'd need nine Michigans to make up for the loss in TX alone.