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Margin of victory analysis for the 2021 state legislative elections
On November 2, 2021, three of the nation's 99 state legislative chambers held regularly-scheduled elections for 220 seats, meaning that 2.9% of all state legislative seats were up for election.
Republicans won a majority in the Virginia House of Delegates, while Democrats held their majorities in the New Jersey General Assembly and the New Jersey State Senate. The change in Virginia broke the state's Democratic state government trifecta and resulted in a divided government.
Across all 220 seats up for election, the average margin of victory was 23.6%. An electoral margin of victory (MOV) is the difference between the share of votes cast for the winning candidate and the second-place candidate in an election. Only races with more than one candidate were included in this average.
On this page, you will find an overview of average margins of victory by chamber, a detailed breakdown of each legislative chamber's margins of victory, and a closer look at the three races decided by margins of 0.5% or smaller.
To learn more about margins of victory in the previous odd-year state legislative elections (2019), click here.
Margin of victory
The margin of victory is the difference between the vote share received by a winning candidate and the runner-up. For example, if Candidate A wins an election with 55 percent of the vote and Candidate B, the second-place finisher, wins 45 percent of the vote, the winner's margin of victory is 10 percent. In chambers with multimember districts, the margin of victory is calculated as the difference between the winning candidate with the fewest votes and the losing candidate with the most votes. Margins of victory can be used to measure electoral competitiveness, political party or candidate strength, and, indirectly, the popularity of a particular policy or set of policies.
Upper chamber average margins of victory
The table below shows the number of seats up for election and the average margin of victory in each state legislative upper chamber.
| Average MOV for state legislative upper chamber elections, 2021 | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Chamber | Seats up for election | Average margin of victory | ||||||||
Lower chamber average margins of victory
The table below shows the number of seats up for election and the average margin of victory in each state legislative lower chamber.
| Average MOV for state legislative lower chamber elections, 2021 | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Chamber | Seats up for election | Average margin of victory | ||||||||
Election results by chamber
The chart below displays the breakdown of races by the winner's partisan affiliation and margin of victory for each state legislative chamber with single-member districts which held elections in 2021. A darker shade of red or blue indicates a larger margin for that party. The table below displays how many seats were up for election in each chamber and how many seats each party won. It also includes a breakdown of how many seats Democrats and Republicans won by 10% or less and without opposition in each chamber, as well as the average margin of victory for each party. Click on a particular header to sort the table.
| Average MOV for state legislative elections, 2021 | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Chamber | Seats up for election |  Seats won by Democrats
|
Seats won by Democrats by margins of 10% or less
|
Seats won by unopposed Democrats
|
Average margin of victory for Democrats
|
 Seats won by Republicans
|
Seats won by Republicans by margins of 10% or less
|
Seats won by unopposed Republicans
|
Average margin of victory for Republicans
|
 Seats won by independent and minor party candidates
|
| New Jersey State Senate | ||||||||||
| New Jersey General Assembly[1] | ||||||||||
| Virginia House of Delegates | ||||||||||
| Total | ||||||||||
State legislative races decided by 0.5% or less
In 2021, there were three races decided by margins of 0.5% or smaller.
| State legislative races decided by 0.5% or less, 2021 | ||||
|---|---|---|---|---|
| District | Winner | Runner-up | Margin (%) | Margin (number of votes) |
| New Jersey General Assembly District 11 | Kim Eulner |
Joann Downey |
||
| Virginia House of Delegates District 91 | Aijalon Cordoza |
Martha Mugler |
||
| Virginia House of Delegates District 85 | Karen Greenhalgh |
Alex Askew |
||
See also
- State legislative elections, 2021
- State legislative special elections, 2021
- Trends in the margins of victory for incumbents of three or more terms, 2018-2024
Footnotes
- ↑ 1.0 1.1 For the purposes of this study, the margin of victory was calculated by comparing the winner with the least votes to the loser of the opposite party with the most votes. Therefore, the numbers will total up to half the seats won for each party since we can only compare MoV for one of the two seats in each district.
