Why are Republicans so much stronger/Democrats weaker at the state level?

[Skill and Chance]

Here is a map of partisan control of the 50 state governments.  Green indicates split control (anything that is not an R or D trifecta).  I have given VA split control in light of Northam's certain LG win and McAuliffe's likely Gov win.

I have given VA split control in light of Northam's certain LG win and McAuliffe's likely Gov win.  Republicans fully control 5 states that voted for Obama twice and 3 states that have not voted Republican for president since 1988.  Yet Democrats only control WV among the 24 Romney states.  And you pretty much only get full Democratic control at the 60% Obama level presidentially.  Do Republicans systematically care more about state level governments?  Is it all about gerrymandering?  Democrats do seem to be systematically better at electing governors than at state legislative control...

[Skill and Chance]

Gerrymandering and gains the GOP made in 2010 are part of the reason, but the more important factor is structural: Democratic voters these days tend to be clumped together into urban areas, while Republican voters tend to be more efficiently distributed throughout rural, exurban and suburban areas. This doesn't make a difference in statewide races (a vote is a vote no matter where it's from) but it does matter when it comes to electing state legislatures.

Democrats have two options if they want to address this. They can either 1) maintain and expand the electoral coalition to bring in more of these voters or 2) end the practice of electing state legislatures based on geography. The first one seems much easier.

Also, the "Democrats only control 1 of the 24 Romney states" fact is a little misleading. Many of those Romney states have very small populations. Someone should tally up the total population of states with a Democratic trifecta vs. states with a Republican trifecta.

The small/large state thing is much less of an issue now than it was 10-20 years ago.  D's have New England just about locked down and are taking over NM, NV and CO.  A tied presidential election would yield 26R/24D in the states now (with the D winning VA by only a couple hundred votes).  Compare that to a tied 2000 PV, where the states would have split 33R/17D (Bush wins OR and everything right of it).  2004 would have been 28R/22D in a tie.  2008 would have been 27R/23D.  And 2012 would be 26R/24D.  Democrats are getting better at winning states in recent years. 

[Skill and Chance]

Gerrymandering and gains the GOP made in 2010 are part of the reason, but the more important factor is structural: Democratic voters these days tend to be clumped together into urban areas, while Republican voters tend to be more efficiently distributed throughout rural, exurban and suburban areas. This doesn't make a difference in statewide races (a vote is a vote no matter where it's from) but it does matter when it comes to electing state legislatures.

Democrats have two options if they want to address this. They can either 1) maintain and expand the electoral coalition to bring in more of these voters or 2) end the practice of electing state legislatures based on geography. The first one seems much easier.

Also, the "Democrats only control 1 of the 24 Romney states" fact is a little misleading. Many of those Romney states have very small populations. Someone should tally up the total population of states with a Democratic trifecta vs. states with a Republican trifecta.

The small/large state thing is much less of an issue now than it was 10-20 years ago.  D's have New England just about locked down and are taking over NM, NV and CO.  A tied presidential election would yield 26R/24D in the states now (with the D winning VA by only a couple hundred votes).  Compare that to a tied 2000 PV, where the states would have split 33R/17D (Bush wins OR and everything right of it).  2004 would have been 28R/22D in a tie.  2008 would have been 27R/23D.  And 2012 would be 26R/24D.  Democrats are getting better at winning states in recent years. 

Ok, but that's more a coincidence of how demographic trends are moving in smaller states, not some sort of improved ability at winning elections by the Democratic Party. And even if the imbalance isn't as great as it used to be, it's still present, which was my point. We should get as much "credit" for having a trifecta in California as they get for having trifectas in North Dakota, South Dakota, Wyoming, Kansas and Oklahoma, Utah and Idaho.

It's more significant than you think.  Democrats have not held the advantage of winning more states in a tie since FDR.  They could very well do that circa 2016/2020 if FL and NC keep moving their way.