Safe Republican (2)
North Dakota - Doug Burgum (R) vs. Marvin Nelson (D) - Republicans rule the Dakotas with an iron fist as of now, although they are sometimes susceptible to electing Democrats down the ticket on occasion (Senator Heidi Heitkamp comes to mind). All the same, no reason to believe this is remotely competitive. And if you think that's bad...
Utah - Gary Herbert (R) vs. Mike Weinholtz (D) - Yeah, even if Clinton were winning the presidential election by 25 points and Democrats were swept into all levels of power, Utah's gubernatorial race would remain firmly Republican.
Tossup (1)
Indiana - John Gregg (D) vs. Eric Holcomb (R) - The incumbent governor, Mike Pence vacated his candidacy to strap himself onboard the Titanic, or should I say the Trump campaign. This gave Gregg a huge advantage as he'd already been in the race for several months whereas Republicans had to scramble for a replacement candidate. Holcomb however seems relatively inoffensive, and Indiana is hardly known for electing Democrats making it hard to see an easy Gregg victory. Gregg's candidacy shouldn't be underestimated, however - he lost to Pence in 2012 by a much smaller-than-expected margin, and sharing the ticket with Evan Bayh will only serve as a boost to his candidacy.
Lean Democratic (5)
Missouri - Chris Koster (D) vs. Eric Greitens (R) - While Missouri - a former bellwether state - has trended Republican very quickly over the past few years, they seem to like their Democratic governors well enough. Koster has maintained a consistent lead in polling, even as it's ranged from small to large, leaving me with the impression he can safely be called the favorite, even if the race can not exactly be called safe.
North Carolina - Roy Cooper (D) vs. Pat McCrory (R) - If there were a premier battleground for gubernatorial contests in 2016 (as there are so few to begin with), North Carolina would have to be it. McCrory's "bathroom bill" has backfired tremendously on the imperiled governor, angering liberal activists and driving businesses out of state. Cooper on the other hand has a solid record as a popular Attorney General for the state, serving since 2001 - he even ran unopposed in 2012. Most Republicans privately concede this one has slipped away.
New Hampshire - Collin Van Ostern (D) vs. Chris Sununu (R) - I admittedly don't know too much about the state of affairs in the New Hampshire gubernatorial race, an open contest after sitting governor Maggie Hassan decided to jump trains and challenge Kelly Ayotte for the state's Senate seat. Assigning it as Lean D can be seen as more of a gut instinct than anything, as the race has only been polled very lightly.
Vermont - Sue Minter (D) vs. Phil Scott (R) - You would think that Vermont, one of the bluest states in the nation would be a lock for Democrats, but the state has flirted with Republicans at the executive level. Scott is the sitting Lieutenant Governor, and has proven quite popular swimming against the tide. If anyone could make this a race, it would be him - but I'd be cautious about assuming too much of his chances running for the most significant statewide position in Vermont.
West Virginia - Jim Justice (D) vs. Bill Cole (R) - A coal baron versus a Cole, and West Virginians would walk across hot coals to vote Republican these days. To put this in perspective, if Donald Trump were to lose in a 1972/1984-style blowout in which he only carried one state, West Virginia would probably be it. All the same, the Democratic Party was in full control of state politics here until very recently, but the tables flipped very quickly and most assumed it would only be a matter of time before Republicans took the governor's mansion. Justice, however has maintained a solid lead in polling, and Republican groups have gone completely dark in this race. For now, it would seem West Virginia Democrats have been given a lifeline.
Likely Democratic (1)
Montana - Steve Bullock (D) vs. Greg Gianforte (R) - Aside from the at-large Congressional district and the presidential elections, Republicans have only won a single statewide race in Montana in the past fourteen years, the open Senate contest in 2014. While the state is quite Republican at the presidential level, Montana Democrats make for an extremely effective (and surprisingly liberal!) state party, and no one seems to be taking this race too seriously. Fun fact: There are currently five Democratic Senators elected in states that Romney carried in 2012, and all five of those states have a gubernatorial election this year. This may provide a glimpse at the 2018 midterm election, which has the makings of a bad night for the Democrats.
Safe Democratic (3)
Delaware - John Carney (D) vs. Colin Bonini (R) - Snoozer, much like the state of Delaware. Sorry Delawareans.
Oregon - Kate Brown (D) vs. Bud Pierce (R) - Brown looked vulnerable at one point as she ascended to the governor's seat through some rather unusual circumstances, but otherwise the race seems safe.
Washington - Jay Inslee (D) vs. Bill Bryant (R) - The Republican nominee here doesn't even have a Wikipedia page, which should indicate how seriously the Republicans are taking this race.
Presidential Ratings (last updated 9/6/2016)
Senate Ratings (last updated 9/13/2016)