Margin of victory analysis for the 2019 state legislative elections

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2019 State Legislative Elections
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2019 elections
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2019 Elections
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On November 5, 2019, seven of the nation's 99 state legislative chambers held regularly-scheduled elections for 538 seats, meaning that 7.3% of all state legislative seats were up for election.

Democrats won majorities in the Virginia State Senate and the Virginia House of Delegates, while holding their majority in the New Jersey General Assembly. The victories in Virginia made the state a Democratic state government trifecta. Republicans held their majorities in the Louisiana State Senate, Louisiana House of Representatives, Mississippi State Senate, and the Mississippi House of Representatives.

Across all 538 seats up for election, the average margin of victory was 26.0%. 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.

HIGHLIGHTS

Major-party candidates won 57 seats by margins of 10% or less; 31 of those seats were won by Democrats and 26 by Republicans.

The average margin of victory was 23.7% for Democrats and 27.7% for Republicans.

The chamber with the smallest average margin of victory in 2019 was the New Jersey General Assembly (14.6%), followed by the Virginia House of Delegates (21.8%) and the Virginia State Senate (27.6%).

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 two races decided by margins of 0.5% or smaller.

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, 2019
Chamber	Seats up for election	Average margin of victory
Louisiana State Senate	39	38.8%
Mississippi State Senate	52	30.2%
Virginia State Senate	40	27.6%

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, 2019
Chamber	Seats up for election	Average margin of victory
Louisiana House of Representatives	105	36.1%
Mississippi House of Representatives	122	32.9%
New Jersey General Assembly	80	14.6%
Virginia House of Delegates	100	21.8%

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 2019. 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, 2019
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
Louisiana State Senate	39	12	0	9	37.3%	27	0	20	39.4%	0
Louisiana House of Representatives	105	35	1	28	31.1%	69	3	48	37.7%	1
Mississippi State Senate	52	16	1	11	33.3%	36	1	23	29.0%	0
Mississippi House of Representatives	122	46	4	38	25.9%	75	2	53	36.3%	1
New Jersey General Assembly	80	52	8	3	17.7%	28	8	0	8.2%	0
Virginia State Senate	40	21	2	10	33.2%	19	5	1	24.2%	0
Virginia House of Delegates	100	55	15	23	20.6%	45	7	8	22.8%	0
Total	538	237	31	122	23.7%	299	26	153	27.7%	2

State legislative races decided by 0.5% or less

In 2019, there were two races decided by margins of 0.5% or smaller.

State legislative races decided by 0.5% or less, 2019
District	Winner	Runner-up	Margin (%)	Margin (number of votes)
Mississippi House of Representatives District 40	Hester Jackson-McCray	Ashley Henley	0.45%	14
Virginia House of Delegates District 83	Nancy Guy	Christopher Stolle	0.12%	27

See also

• State legislative elections, 2019
• State legislative special elections, 2019
• Trends in the margins of victory for incumbents of three or more terms, 2018-2024