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Did gerrymandering hurt Democrats down ballot in 2020? Yes and no

Ballot roll-off, ticket splitting among several factors that prevented party from flipping targeted state chambers

Voters stand in line on the last day of early voting at Lenora Park Gym in Snellville, Ga., on Oct. 30. Democrats came up short in their attempt to flip the Georgia state House and all other targeted state chambers.
Voters stand in line on the last day of early voting at Lenora Park Gym in Snellville, Ga., on Oct. 30. Democrats came up short in their attempt to flip the Georgia state House and all other targeted state chambers. (Tom Williams/CQ Roll Call file photo)

Joe Biden may have won the presidency by a decisive margin in the popular vote and Electoral College, but none of the state chambers targeted by Democrats flipped blue in 2020. In fact, the party lost ground in some chambers, including the North Carolina House. Further, states like Pennsylvania and Arizona that went to Biden saw Democrats in the state legislature receive a smaller share of the vote than their Republican counterparts.

Let’s explore a few factors that may have influenced these outcomes: gerrymandering, ballot roll-off and ticket splitting, as well as an enthusiasm or awareness gap between presidential and state legislative candidates.


Gerrymandering — the drawing of legislative and congressional districts in a way that provides an advantage to the party in power — may account for some of this year’s state legislative results. If these chambers were affected by gerrymandering, we would expect Democrats at the legislative level to have received more votes than Republicans but to have won fewer seats. One way to look at this is a ‘seat share gap,’ a measure that indicates how big the gap is between the percentage of seats Democrats should have won (based on their chamber-wide vote total) and the percentage of seats they will actually occupy postelection.

We investigated this for several state chambers targeted by Democrats this year.

As the table indicates, in the Michigan House and Minnesota Senate, the seat share gaps were somewhat small in absolute terms, but large enough for Republicans to retain both chambers, which Democrats would have flipped, or at least tied, under fairer maps.

In other chambers, seat share gaps were particularly egregious and clearly indicate that gerrymandering led to Democrats winning fewer seats than they earned in the chamber-wide vote share. For instance, Democrats won 49.04 percent of the vote in the North Carolina House but will hold only 42.5 percent of the seats (a gap of 6.54 percent). In the Wisconsin State Assembly, Democrats won 45.29 percent of the vote but will only hold 38.28 percent of the seats (a gap of 7.01 percent). 

But although gerrymandering, measured by chamber-wide seat share gaps, often resulted in Democrats holding fewer seats than they earned, there was only one chamber (the Minnesota Senate) where Democrats earned a significantly greater share of the vote than Republicans but failed to win control.

Ballot roll-off and ticket splitting

Ballot roll-off refers to the phenomenon where people vote for candidates at the top of the ticket but ignore down-ballot candidates, such as those in state legislative races. If roll-off contributed to the 2020 legislative outcomes, we would expect Democratic legislative candidates to have received significantly fewer overall votes than Democrats at the top of the ticket. 

There is a good amount of evidence that this is what happened. State legislative Democrats did not receive more votes than Biden in any chamber we looked at. This gap was particularly pronounced in the Pennsylvania House, where Democratic legislative candidates received 419,191 fewer votes than Biden; the Texas House, where they received 738,490 fewer votes; and the Florida House, where they received 1.5 million+ fewer votes. It is clear that in some states, Biden voters either rolled off the ballot or they split their tickets and voted for Republicans at the legislative level. 

And ticket splitting clearly contributed to the GOP advantage in this year’s state legislative outcomes. Republican legislative candidates outperformed Donald Trump in four key states that went to Biden: In Minnesota, 48,956 more voters cast ballots for Republican state Senate candidates than for Trump; in Michigan, 3,751 more voters cast ballots for Republican state House candidates; in Wisconsin, 55,507 more voters cast ballots for Republican candidates for the state Assembly; and in Pennsylvania, 16,679 more voters cast ballots for Republican state House candidates. While these don’t seem like large differences, many state legislative races are won by tiny margins (sometimes, just a single vote).

Enthusiasm or awareness gap

The enthusiasm or awareness gap between voters for the top and bottom of the ticket can also be expressed as a lack of “coattails” for down-ballot candidates from up-ballot partymates in higher-profile races. In all of the chambers we investigated, Republicans running for state legislature received a higher percentage of the vote total than Trump. On the flipside, Democratic legislative candidates in all of these chambers, except the North Carolina House, received a lower percentage of the vote than Biden. 

This indicates that Biden lacked coattails, which would have allowed down-ballot candidates to benefit from the relatively higher presidential turnout and ride those coattails to victory (or at least a higher vote share).

Bottom line

While none of these things alone can account for what we saw in 2020, it is clear that all of these factors may have contributed to the lopsided Democratic defeats in legislative chambers across the country despite Biden’s decisive victory.

Our analysis aims to describe what happened, but not why the outcomes occurred. The party and movement partners will need to untangle the why by examining the resonance of Democratic messaging, the impact of the pandemic on Democratic field programs, the impact of misinformation, voter suppression tactics and other factors.

For transparency, we are linking to our dataset, which we constructed based on publicly available voting information.

Gaby Goldstein is the director of research at Sister District Action Network, the nonprofit arm of the Sister District Project, a women-led grassroots organization that helps elect Democrats to state legislatures.

Mallory Roman is the associate director of research at Sister District Action Network.

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