In the gubernatorial races, the overexposure is almost exactly flipped: Republicans will be defending nine governorships in states Clinton won — Illinois, Maine, Massachusetts, Maryland, New Hampshire, New Jersey, New Mexico, Nevada, and Vermont — while Democrats will be defending just one governorship in a Trump-won state (Pennsylvania).
So Democrats are hoping that they can win a substantial number of governorships over the next two years, given how many open seats the GOP is defending and the general tendency for the party that does not hold the White House to make gains down the ticket in a midterm year. The president’s party has netted governorships only once (1986) in 18 postwar midterms. As of now, we favor the Democrats in two Republican-held seats — New Jersey and New Mexico. Overall, the Democrats should start 2019 with more governorships than they hold now, but the high number of Toss-ups and otherwise potentially very competitive races combined with the unsettled national environment next year creates a high degree of uncertainty.
Source: Sabato's Crystal Ball
Geoffrey Skelley and Kyle Kondik have introduced CB’s initial ratings for the 2017/2018 Gubernatorial contests, and the overall landscape could prove fruitful for Democrats. Republicans hold a near-record level of mansions right now, and like scaling a mountain, eventually there’s nothing left to climb. The only pickup opportunities for them appear in Connecticut (whose current Governor, Dan Malloy, will not run for re-election), Colorado, and Minnesota. Meanwhile, Republicans have twenty-eight contests to defend. While favored in a majority of them (including Texas, Oklahoma, and South Carolina), Skelley and Kondik rate two as probable Democratic gains (New Mexico and New Jersey) and another five as toss-ups.
The only race I’d take issue with them on is Wisconsin. While Governor Walker has never won a race with a double-digit margin, and has rather blah approval ratings right now, every big name Democrat has already passed over the contest. It should be a close race, but it won’t without a candidate. He’s a strong favorite until someone actually declares against him. I’m more pessimistic on Republican Senatorial gains for a similar reason: until someone declares against an incumbent, the sitting Senator start off as the favorite.