Split Ticket’s new Congressional Voting Index (CVI) gauges each House district’s partisan lean. In contrast to counterparts like Cook PVI, our CVI uses a unique methodology that makes it more representative of the current electoral climate. This tool will improve our 2024 House ratings by shedding light on how seats may be expected to vote after accounting for candidate-driven effects and the national environment.
Our CVI builds off of three previous projects: the 2022 House WAR model, the SHAVE metric, and the Trend Score index. The first tool provides adjusted district partisanships for the last two presidential elections as well as candidate-independent 2022 House results estimates for every seat. The second allows us to predict how uncontested seats might have voted, relative to state-level environments in a given cycle, had they been contested by Republican and Democratic nominees. The last quantifies the direction in which individual House seats are trending and how unrealized shifts impact flippability. A browsable table with per-district CVI scores is available here and at the bottom of this article (best viewed on Desktop).
Our CVI can be found on our website. Each district is placed into one of seven categories based on calculated partisanships. Associated score ranges are defined below.
There are obviously too many CVI leans to discuss in one article, so we decided to break down important House generalities based on the categories provided below. Holistic analysis allows us to see which party would have an inherent advantage in the House based on our leans alone. Viewing federal partisanship without candidate-driven distortions helps determine how competitive the redistricted House map really is.
If every seat were assigned by its CVI split, Democrats would control 218 to the Republicans’ 217 – an even narrower majority than the one currently held by the GOP. Of the 435 districts, 314 are rated either Firmly D/R, meaning they lean toward either party by at least 15 points and are not considered competitive. 121 seats are classified as Even, Moderately D/R, or Mostly D/R.
Of those districts, the 22 in the Even group form the so-called “competitive core” of the House playing field. With minor exceptions like PA-01, where GOP incumbent Brian Fitzpatrick is formidable, these districts should be the chamber’s most volatile from cycle to cycle. A quick look at our Flip Index shows predictable overlap.
The Democrats’ 218 to 217 CVI majority also seems to confirm prior Split Ticket research which found that the recently-redistricted House map may have a D+1 House bias, a far cry from the that of the gerrymandered Republican lines pioneered by Project REDMAP in 2012. Our 218th seat, New York’s 19th district, has a D+0.6 partisanship, suggesting the chamber does indeed align with last year’s estimates.
The 19th (Biden +4.6) may not be a cross-section of America, but it is an excellent embodiment of the traditionally-Republican, Democratic-trending swing seats which now sustain the GOP’s narrow 222-213 majority. Republican Marc Molinaro flipped this open district last November after losing an August special election to Democrat Pat Ryan. Whether or not he wins reelection in the median seat with President Joe Biden on the ballot should be an excellent bellwether for overall House control.
As we alluded to above, the threadbare Republican House majority currently relies on a dozen moderate and center-right incumbents representing districts won by Joe Biden in 2020. In other words, ticket splitting evoked by specific candidates, like Molinaro, helped the GOP secure control of a chamber that Democrats would be expected to win with generic candidates under neutral environmental conditions.
To get an early look at how vulnerable the Republicans’ majority will be to the effects of presidential turnout and polarization in 2024, we tallied the number of crossover seats based on our CVI, not 2020 presidential, to divide up the Republican and Democratic conferences into each of the seven classifications defined previously. This allows us to predict, for example, the most vulnerable districts held by both parties based on partisanship alone. Keep in mind that incumbency and candidate effects will be factored into our eventual ratings.
We define a crossover incumbent as a member representing a seat that leans toward the opposite party. There are 21 of these representatives under the CVI, 11 of whom represent “Even” districts. The long-term vulnerabilities of the GOP House majority become quite apparent when one considers that 13 of the 21 total crossover districts (62%) are held by Republican incumbents; seven of them won marginal Biden seats, like NY-19, in 2022, all of which will be high on Democratic target lists next year.
Among those seats rated Moderately D/R and Mostly D/R, which sometimes favor the minority party due to candidate quality deltas, House Republicans are stretched even thinner. They have six crossover seats across the two categories compared to the Democrats’ four. Six of these ten members are also freshmen, though Mary Peltola (AK-AL) did win an August special election before securing a full term.
A final thorn in the Republicans’ side is the experience of their crossover candidates in seats with particularly-hostile partisanships. While incumbents like Mike Garcia (CA-27) and David Valadao (CA-22) have proved their strength in multiple difficult cycles, newer members such as Anthony D’Esposito (NY-04) and Mike Lawler (NY-17) remain untested in presidential years. Democrats like Matt Cartwright (PA-08) and Jared Golden (ME-02), by contrast, have clear records of electoral success in Trump-won seats.
Assuming the national environment is more Democratic in 2024 than it was in 2022, our numbers suggest that Republicans, particularly those crossover freshmen elected narrowly last fall, will be on the offensive in a TOSSUP House chamber. House bias may favor Democrats slightly (D+0.5), but a 218-217 majority is effectively a dead heat. We consider this a fair median case given higher levels of expected voter turnout and accompanying presidential-year polarization.
While we think it’s possible for Democrats to end up with a larger margin of victory, especially if former President Donald Trump drags down Republicans like Marc Molinaro as the 2024 GOP nominee, there is currently not enough evidence to suggest either party is favored in the chamber.
Democratic success will depend on recruitment in individual races, shrewd spending decisions, favorable state-level political environments, ineffectual mid-decade redistricting, and the Republicans’ presidential nominee. At the minimum, Democrats are expected to devote more time, money, and interest to seats in which they narrowly came up short last November like AZ-01, AZ-06, MI-10, and CA-41.
Let’s now break down the methodology underlying our CVI. We collected four results variables for each of the nation’s 435 House seats: 2020 presidential, 2022 congressional, 2024 estimated, and 2016 presidential. They received weights of 50%, 25%, 15%, and 10%, respectively. To ensure an even national environment in our calculations, we shifted all WAR model data uniformly based on the cycle.
Weight assignments reduced the effects of recency bias and elastic midterm phenomena like down-ballot lag. We chose to avoid state-level returns (i.e., gubernatorial results) for the sake of consistency and relevance to national dynamics, as the CVI is intended to be a federal election metric. The lack of uniform statewide data also drove us to exclude numbers from 2018.
The 2020 and 2016 district-by-district presidential results are internally-consistent with the other WAR model data and account for differing national environments. 2020’s returns receive significantly more weight than 2016’s in the CVI because they are more recent and, therefore, the better gauge of potential 2024 coalitions in swing districts – even if Democrats lose the White House.
Hillary Clinton’s 2016 win in Mahoning County (OH), for example, could not be replicated by Joe Biden in 2020 or even Senate nominee Tim Ryan in 2022, suggesting that placing too much emphasis on 2016 could overstate the strength of both parties’ historical coalitions ex post facto. That said, anomalies like Republican Glenn Youngkin’s victory in Virginia’s 2021 gubernatorial race should remind us that trends are not linear. In other words, 2016 numbers are still meaningful enough to be included in our calculations to a minor extent.
The variable receiving the second-most weight after 2020 adjusted presidential lean is 2022 wins-above-replacement (WAR) predicted, which controls for candidate-driven variations in the actual midterm results by calculating how generic Republican and Democratic candidates would have been expected to perform in each House district. 2022 SHAVE estimates filled in the gaps for uncontested seats where WAR findings could not be applied. All values were shifted leftward by 1.6 points to control for the national environment.
We account for candidate quality deltas in our CVI scores because they are designed to accurately quantify each seat’s baseline partisan lean void of effects related to the strengths and weaknesses of specific nominees. Had we, for instance, not controlled for Democratic Rep. Marcy Kaptur’s 16-point overperformance in OH-09, a Trump-won seat, the district’s calculated partisan lean would have been embarrassingly misrepresentative of political realities.
The final piece of the methodological puzzle comes from our set of Trend & Flip Scores, which can be found here. While last month’s Trend Scores do utilize the actual 2016 and 2020 presidential results, applying the adjusted WAR numbers to the underlying formula does not significantly change any outcomes. We derive our estimated 2024 leans by shifting 2020 toplines based on each district’s Trend Score. By putting slightly more weight on where a seat is going (2024) than where it has been (2016), we believe our CVI scores become more circumspect.
There are, however, a few caveats worth mentioning as we head into the 2023-2024 cycle. Mid-decade redistricting is set to take place in North Carolina and Ohio, with rumors of a Texas redraw also in the mix. A recent court decision additionally struck down South Carolina’s 1st district following a racial discrimination lawsuit, which would force changes to the Palmetto State’s congressional lines should SCOTUS let it stand. Split Ticket’s CVI will be updated as soon as new maps are approved for the upcoming cycle. Revised methodology will be used when necessary.
The Split Ticket CVI received a minor data update on March 7th.
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My name is Harrison Lavelle and I am a political analyst studying political science and international studies at the College of New Jersey. As a co-founder and partner at Split Ticket, I coordinate our House coverage. I write about a variety of electoral topics and produce political maps. Besides elections, my hobbies include music, history, language, aviation, and fitness.
Contact me at @HWLavelleMaps or firstname.lastname@example.org
I’m a software engineer and a computer scientist (UC Berkeley class of 2019 BA, class of 2020 MS) who has an interest in machine learning, politics, and electoral data. I’m a partner at Split Ticket, handle our Senate races, and make many kinds of electoral models.