The midterm electorate is skewed far to the right. Only 13 governors are elected by presidential electorate, while 36 are elected by midterm electorates and 1(Va.) elected the year following each presidential election(an even smaller electorate). The results of this is far reaching and can be remedied to a large extent.
Governors have great power in signing or vetoing laws, setting executive branch policy, and appointing individuals to very powerful boards and positions of influence. The secretary of state exerts great control over access to the ballot box. The attorney general and treasurer also exert great influence and power over state government.
Further, the apportionment boards of many states, who wield the power to gerrymander state and federal congressional districts as they choose, is very oftentimes dominated by the executive branch members. So the election of the executive branch is also determinative the the type of legislature a state will have.
The vast majority of the states elect the executive branches during the midterm elections and, as a result, their state executive branches and legislatures(by means of gerrymandering) are skewed far to the right and not reflective of the state as a whole.
This is a very difficult problem in many states but, in some, this could be very easily remedied. Fourteen states have both a constitutional amendment process and elect their executive branch during midterm elections. They are as follows: AZ, AR, CA, CO, FL, IL, MA, MI, NE, NV, OH, OK, OR and SD. It would be a relatively straightforward and difficult to distort amendment necessary to make the 2018 election a 2-year term and elections from 2020 forward 4-year terms for these states' executive branch members. It is straightforward argument: let's elect the governor when all the voters vote. I think voters would prefer to be able to elect the president and governor at the same time.
Imagine an Ohio, Michigan, or Florida in which the executive branch members were elected by the 2008 and 2012 electorates, as opposed to the 2010 and 2014 electorates. Imagine the magnitude of the different policy decisions that would have been made in these states(medicaid expansion, right-to-work, voter suppression, etc…). Think about the net changes in US House seats were the districts drawn in these 14 states by executive branch members elected in 2020, as opposed to 2018.
This would be a one-time investment by the Democratic Party and progressive groups that would pay huge dividends indefinitely. And, if their smart, it's an investment they'll make.