Electoral competitiveness in Illinois, 1912-2014

Competitiveness in state legislatures
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Published in April 2015

The 2014 national election continued the decline in U.S. electoral competitiveness that has occurred since 1972. The decline of electoral competitiveness that has been seen on the national stage, has also been seen in states. For example, the percentage of elections won by less than 10 percent or less in the Illinois State Senate decreased from 50 percent in 1968 to 10.5 percent in 2014.

This page contains electoral competitiveness information at various levels of government in this state up to 2014. For more recent information about state legislative competitiveness nationwide, click here.

The data presented below are part of a larger project on electoral competitiveness, the full report is available in the table to the right. The images below illustrate the changes in the competitiveness of elections in Illinois from 1912 through 2014. The data used to generate these graphs is available in the tables below those images.

Background

Since 1972, electoral competitiveness has tended to decrease across the United States. During that time, people who are members of the same political party have become more likely to live in the same area as one another than in the past. Nationally, the rate at which incumbents won reelection is also close to an all-time high. However, this does not have to do with incumbents deriving more advantages from holding office than before. It is because they are more likely to be in safe districts for their party. In contrast to the high incumbency reelection rate, the rate at which incumbents run for reelection has gone down over time.

Competitiveness is declining. On the national level, the percentage of state legislative elections won by 5 percent or less was nearly the lowest in the 1972 to 2014 period. In an absolute sense, the incidence of such elections was very low. Only 4.9 percent of U.S. residents in districts with elections saw their election won by 5 percent or less. Similarly, more Americans lived in areas with uncontested elections than ever before in the time period studied: 36.7 percent. State legislative primaries were often found to be won by wide margins or not contested at all. The rate at which incumbents won reelection is also close to an all-time high. However, this does not have to do with incumbents deriving more advantages from holding office than before. It is because they are more likely to be in safe districts for their party. In contrast to the high incumbency reelection rate, the rate at which incumbents run for reelection has gone down over time.

Competitiveness in elections in Illinois

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  [Ballot_StateGraph01_Marg_Stateno13Illinois2015_04_23.png|Marginal Elections]

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  [Ballot_StateGraph02_Uncont_Stateno13Illinois2015_04_23.png|Uncontested Elections]

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  [Ballot_StateGraph03_Inc_Stateno13Illinois2015_04_23.png|Incumbent Win Rates]

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  [Ballot_StateGraph04_US_HS_Stateno13Illinois2015_04_23.png|Competitiveness in U.S. House Seats]

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  [Ballot_StateGraph05_UpBallot_Stateno13Illinois2015_04_23.png|Margin of Victory in Up Ballot Elections]

Table explanation

The columns in the tables below for both state senates and state houses are as follow:

• Seats: number of seats in the state legislative chamber.
• Percent Seats Up: percent of seats in the state legislative chamber that are up in a particular year for the November election.
• Percent Won By Dem: the percent of seats in the state legislature that were won by a Democrat.
• Percent Unusable: percent of seats for the state legislative chamber that weren’t usable to compute whether a race was marginal or not for this chamber in this year because of missing data. This column usually says “0.”
• Percent with 5% margin: percent of seats for a state chamber in a year that were won by 5% or less.
• Percent with 10% margin: percent of seats for a state chamber in a year that were won by 10% or less.
• Percent Unusable Other: percent of seats that have missing data that prevent the computation of whether an incumbent won or lost, whether an incumbent ran or not, or whether a race was uncontested. This column usually says “0.”
• Percent Uncontested: percent of races in a chamber that are uncontested.
• Percent Incumbent Win: percent of incumbents who ran for a state chamber in a particular year who won.
• Percent With Incumbent: number of incumbents running for reelection for a state-chamber in one year, divided by the number of seats that are up for election for that state-chamber, multiplied by 100.

The columns for the “Up ballot” tab are as follows:

• U.S. House Seats: number of U.S. House Seats that a state was apportioned in the year in question.
• Percent Not Usable: percent of U.S. House Seats in the state and year that aren’t usable to compute marginality or contestation, because of something unusual about the race.
• Percent With 5% Margin: percent of U.S. House races in the state and year that were won by 5% or less.
• Percent With 10% Margin: percent of U.S. House races in the state and year that were won by 10% or less.
• Percent Uncontested: percent of U.S. House races that were uncontested in the state and year.
• U.S. Senate 1 Margin: difference between the percent obtained by the winner of the U.S. Senate election with the U.S. Senate candidate receiving the second most votes.
• U.S. Senate 2 Margin: This is only recorded when a second election to the U.S. Senate was held because of a Senator not completing their term. For such elections, this is the difference between the percent obtained by the winner of the U.S. Senate election with the U.S. Senate candidate receiving the second most votes.
• President margin: difference between the percent of votes obtained by the presidential candidate receiving the most votes in a state minus the percent of votes obtained by the presidential candidate receiving the second most votes in a state.
• Governor margin: difference between the percent obtained by the winner of the gubernatorial election in a state with the gubernatorial candidate receiving the second most votes.

State Senate

State Senate competitiveness, Illinois
Year	Seats	% Seats up	% Won by Dem	% Unusable	% With 5% margin	% With 10% margin	% Unusuable other	% Uncontested	% Incumbent win	% With incumbent	% of Dem inc winning	% of Repub inc winning
1968	58	3.4	50	0	0	50	0	0		0
1970	58	100	50	0	13.8	25.9	0	1.7	85.1	81	100	78.8
1972	59	100	49.2	0	8.5	25.4	0	1.7	94.7	64.4	95.2	94.1
1974	59	33.9	65	0	25	40	0	5	75	80	100	55.6
1976	59	67.8	55	0	10	17.5	0	7.5	92.3	65	92.9	91.7
1978	59	67.8	50	0	7.5	10	0	15	96.6	72.5	93.3	100
1980	59	33.9	50	0	10	20	0	10	92.3	65	88.9	100
1982	59	100	55.9	0	5.1	11.9	0	20.3	90.9	74.6	95.8	89.5
1984	59	35.6	47.6	0	4.8	14.3	0	23.8	94.1	81	90	100
1986	59	67.8	57.5	0	2.5	10	0	27.5	93.3	75	94.1	92.3
1988	59	66.1	53.8	0	2.6	7.7	0	23.1	100	100	100	100
1990	59	33.9	50	0	5	5	0	35	100	90	100	100
1992	59	100	45.8	0	6.8	11.9	0	30.5	94.4	61	94.1	94.7
1994	59	33.9	45	0	5	10	0	35	94.1	85	87.5	100
1996	59	67.8	50	0	10	12.5	0	45	96.9	80	100	94.1
1998	59	69.5	43.9	0	0	7.3	0	51.2	100	82.9	100	100
2000	59	32.2	47.4	0	10.5	10.5	0	47.4	100	89.5	100	100
2002	59	100	54.2	0	5.1	8.5	0	52.5	90.7	72.9	91.3	90
2004	59	39	56.5	0	4.3	8.7	0	52.2	94.1	73.9	90.9	100
2006	59	66.1	66.7	0	10.3	15.4	0	35.9	100	69.2	100	100
2008	59	67.8	60	0	2.5	5	0	52.5	100	87.5	100	100
2010	59	35.6	57.1	0	9.5	19	0	28.6	88.9	85.7	83.3	100
2012	59	100	67.8	0	3.4	11.9	0	50.8	97.5	67.8	100	92.3
2014	59	32.2	57.9	0	5.3	10.5	0	63.2	94.4	94.7	91.7	100

State House

State House competitiveness, Illinois
Year	Seats	% Seats up	% Won by Dem	% Unusable	% With 5% margin	% With 10% margin	% Unusuable other	% Uncontested	% Incumbent win	% With incumbent	% of Dem inc winning	% of Repub inc winning
1968	177	100	46.3	0	7.3	11.3	0	78	96.6	81.9	96.8	97.6
1970	177	100	49.2	0	2.8	7.9	0	84.2	97.9	81.9	100	96.2
1972	177	100	49.2	0	5.6	11.9	0	66.7	95.3	71.8	100	90.3
1974	177	100	55.4	0	6.2	13.6	0	63.3	93.8	82.5	100	87.5
1976	177	100	52.5	0	4.5	8.5	0	66.7	96.4	78.5	94.7	98.4
1978	177	100	49.7	0	6.8	8.5	0	66.7	93.9	83.1	94.5	95.8
1980	177	100	48	0	4.5	7.3	0	67.8	93.2	83.6	92.2	97.1
1982	118	100	59.3	0	6.8	15.3	0	22.9	80.2	89.8	91.2	70.2
1984	118	100	56.8	0	2.5	10.2	0	33.1	95.9	82.2	93.5	100
1986	118	100	56.8	0	5.1	9.3	0	20.3	99	83.1	98.3	100
1988	118	100	56.8	0	4.2	8.5	0	22.9	98.2	94.1	98.4	98
1990	118	100	60.2	0	2.5	5.1	0	42.4	95.2	88.1	98.3	91.1
1992	118	100	56.8	0	9.3	16.9	0	16.1	89.6	65.3	90.2	88.5
1994	118	100	45.8	0	7.6	11	0	29.7	88.2	86.4	78.2	100
1996	118	100	50.8	0	7.6	14.4	0	27.1	96.1	87.3	100	92.9
1998	118	100	52.5	0	2.5	8.5	0	50	100	83.9	100	100
2000	118	100	52.5	0	3.4	5.1	0	50.8	100	90.7	100	100
2002	118	100	55.9	0	1.7	8.5	0	37.3	96.7	77.1	98	95.1
2004	118	100	55.1	0	2.5	6.8	0	50.8	97.1	89	96.6	97.8
2006	118	100	55.9	0	4.2	7.6	0	50.8	99	89	100	97.8
2008	118	100	59.3	0	5.9	10.2	0	51.7	97.2	90.7	100	95.7
2010	118	100	54.2	0	4.2	9.3	0	42.4	94.9	83.9	91.1	100
2012	118	100	60.2	0	2.5	5.1	0	58.5	95.5	74.6	100	90
2014	118	100	60.2	0	5.1	9.3	0	59.3	100	81.4	100	100

Up ballot

Up ballot competitiveness, Illinois
Year	U.S. House Seats	% Not usable	% With 5% margin	% With 10% margin	% Uncontested	U.S. Senate 1 margin	U.S. Senate 2 margin	President margin	Governor margin
1912								2.3
1916								9.6
1920								45.3
1924								43.2
1928								14.8
1932								13.6
1936								18.5	10.3
1940						0.5		2.4	6.2
1942						6.8
1944						5.6		3.5	1.8
1946	26	0	15.4	19.2	0
1948	26	0	26.9	50	0	10.5		0.8	14.6
1950	26	0	7.7	19.2	0	8.2
1952	25	0	12	16	0			9.9	5.2
1954	25	0	8	28	4	7.1
1956	25	0	4	24	0	8.4		19.3	0.9
1958	25	0	12	20	0
1960	25	0	16	28	0	9.5		0.2	11.2
1962	24	0	8.3	20.8	0	5.7
1964	24	0	4.2	20.8	0			18.9	3.8
1966	24	0	12.5	12.5	0	11.2
1968	24	0	0	12.5	0	6.4		3.2	2.7
1970	24	0	0	4.2	0	15.2
1972	24	0	4.2	12.5	8.3	25		18.6	1.7
1974	24	0	8.3	33.3	4.2	25.1
1976	24	0	4.2	8.3	0			2	30.2
1978	24	0	4.2	8.3	4.2	8			19.1
1980	24	0	4.2	4.2	0	13.7		8.7
1982	22	4.5	14.3	23.8	0				0.1
1984	22	0	9.1	9.1	4.5	1.9		12.9
1986	22	0	13.6	18.2	4.5	31.7			13.7
1988	22	0	4.5	13.6	4.5			2.1
1990	22	0	0	9.1	22.7	30.1			2.6
1992	20	0	0	0	0	10.6		17.2
1994	20	0	0	20	5				29.9
1996	20	0	15	15	10	15.9		19.2
1998	20	0	5	5	20	3			3.6
2000	20	5	5.3	15.8	10			12.4
2002	19	0	0	5.3	10.5	22.7			7.3
2004	19	0	5.3	5.3	5.3	44.2		10.4
2006	19	0	5.3	15.8	5.3				11.8
2008	19	0	0	5.3	5.3	40.8		25.5
2010	19	0	10.5	15.8	0	1.7			0.9
2012	18	0	11.1	27.8	0			17.2
2014	18	0	5.6	11.1	0	11.3			4.1

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