Why do Democrats do systematically better in lower houses of state legislatures?

[Skill and Chance]

Nationwide, Republicans have a 54%/43% seat lead in upper chambers/state senates but only a 51%/48% lead in lower chambers/state houses.  Sure, there are a couple of states like NY where Democrats drew the lower chamber's map and Republicans drew the upper chamber's map, and strong Republican Nebraska's single chamber counts as a state senate, but this is now true even in VA, where Democrats drew (most of) the State Senate map (now 21D/19R) and Republicans drew (most of) the House of Delegates map (now 55D/45R).   It's true in CA, WA, and AZ as well, where an independent process drew the maps.  This also appears to be the case throughout the South, where Republicans controlled the process in nearly every state.  The only place where Democrats do better in state senates seems to be the Northeast, and in Florida, which is very Northeast-influenced.

What is going on here?

[lfromnj]

Nh doesnt hurt. It's like a whole 2 or 3% advantage for Democrats rn despite being around 2% off the us population.

[Skill and Chance]

Nh doesnt hurt. It's like a whole 2 or 3% advantage for Democrats rn despite being around 2% off the us population.

Yes, but this was true prior to 2018 as well. I believe has been true for the entire decade.

[Orser67]

I'm wondering if it has something to do with fact that many of them are only up for election in mid-terms rather than presidential election years, and over the last decade Democrats have generally had a better environment in presidential election years than in mid-terms.

Obviously Democrats just had a strong mid-term year, but it seems possible that Republicans were able to build up incumbency through the 2010 and 2014 elections and thereby survived the 2018 elections.

And on the flip side, a lot of state senators weren't up for election in 2018 and didn't just have to face the worst Republican environment in a decade.

[voice_of_resistance]

Also not talked about is the fact that lower houses tend to have more seats which better reflect the more urban nature of the Democratic coalition these days - state Senates are much easier to rig (take a look at the US Senate vs US House dichotomy). I know that Reynolds v Sims made it so that State Senate districts have to be equal population but the general principle still stands.

[○∙◄☻¥tπ[╪AV┼cVê└]

In NY, the Senate was gerrymandered R while the Assembly was gerrymandered D.

[Beet]

Here in Texas, the state constitution requires that House districts preserve county lines where possible. That means if the Democrats are dominating, say, Big Urban County, they will pick up a bunch of seats in said county. With the state Senate though, you could have one district snaking from Austin to Mexico.

[Pollster]

A few reasons, most of which were mentioned here already:

-Lower chamber districts are smaller and therefore give more favor to voters that self-pack in densely populated areas.

-Lower chamber seats are usually up for election more frequently and therefore tend to be more responsive to changes in the national (and local) mood and realigning coalitions.

-Because many lower chamber districts cover such a small number of voters relatively, it can be a lot harder for gerrymanders to survive waves, swings, trends, and poor candidate quality (often a combination of all four) since flipping a district requires flipping a smaller number of voters.

-States are responsible with coming up for their own rules n how state legislative districts are drawn and how members are elected. In any states, off the top of my head Texas and Massachusetts, these rules tend to favor larger urban areas in the lower chamber.

-Similarly, districts with smaller numbers of voters overall can be easier to microtarget and retail campaign in. It also allows well-known local leaders and popular members of the community to run in uniquely nonpartisan ways (outside of the ways we are used to seeing at the national level).

-Many lower chamber legislators, especially those in machine states, tend to be DINO's and RINO's who run with the full support of the opposing party's bosses, usually to punish other legislators and occasionally governors/AG's who "misbehave."

-Similarly, national political polarization often overshadows a lot of bipartisan work that occurs at the state level. Moderates in both parties are incredibly common in state legislatures, and most stay there because it is increasingly difficult for them to forge paths to higher office in polarized times. Especially in the midwest and New England, there are many Republican state legislators who are strong allies of Democratic governors, and vice versa. These alliances are valuable for fundraising and for on-the-ground campaigns in general.

[Suburbia]

Democrats do well in lower houses because of more density.

That should not excuse Democrats from doing well in upper Houses.

Don't abolish the Senate, compete and contest.

[brucejoel99]

More seats = more opportunities for performing well.

[Skill and Chance]

Democrats do well in lower houses because of more density.

That should not excuse Democrats from doing well in upper Houses.

Don't abolish the Senate, compete and contest.

State senates must have equal population districts as it is, so this doesn't explain it. 

[Del Tachi]

Lower house districts have smaller populations, which gives more of an opportunity for idiosyncratic populations (i.e., racial minorities, urban communities) who typically favor Democrats to constitute an electoral majority.

[SInNYC]

A few reasons, most of which were mentioned here already:

-Lower chamber districts are smaller and therefore give more favor to voters that self-pack in densely populated areas.

-Lower chamber seats are usually up for election more frequently and therefore tend to be more responsive to changes in the national (and local) mood and realigning coalitions.

-Because many lower chamber districts cover such a small number of voters relatively, it can be a lot harder for gerrymanders to survive waves, swings, trends, and poor candidate quality (often a combination of all four) since flipping a district requires flipping a smaller number of voters.

-States are responsible with coming up for their own rules n how state legislative districts are drawn and how members are elected. In any states, off the top of my head Texas and Massachusetts, these rules tend to favor larger urban areas in the lower chamber.

-Similarly, districts with smaller numbers of voters overall can be easier to microtarget and retail campaign in. It also allows well-known local leaders and popular members of the community to run in uniquely nonpartisan ways (outside of the ways we are used to seeing at the national level).

-Many lower chamber legislators, especially those in machine states, tend to be DINO's and RINO's who run with the full support of the opposing party's bosses, usually to punish other legislators and occasionally governors/AG's who "misbehave."

-Similarly, national political polarization often overshadows a lot of bipartisan work that occurs at the state level. Moderates in both parties are incredibly common in state legislatures, and most stay there because it is increasingly difficult for them to forge paths to higher office in polarized times. Especially in the midwest and New England, there are many Republican state legislators who are strong allies of Democratic governors, and vice versa. These alliances are valuable for fundraising and for on-the-ground campaigns in general.

Also, Republicans often portray Democrats as un-American or in some way foreign to the constituency. This is harder to do when the politician in question is actually known to the locals, as might be the case for smaller districts.