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.
% Seats Up: percent of seats in the state legislative chamber that are up in a particular year for the November election.
% Won By Dem: the percent of seats in the state legislature that were won by a Democrat.
% 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.”
% with 5% margin: percent of seats for a state chamber in a year that were won by 5% or less.
% with 10% margin: percent of seats for a state chamber in a year that were won by 10% or less.
% 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.”
% Uncontested: percent of races in a chamber that are uncontested.
% Incumbent Win: percent of incumbents who ran for a state chamber in a particular year who won.
% 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.
% 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.
% With 5% Margin: percent of U.S. House races in the state and year that were won by 5% or less.
% With 10% Margin: percent of U.S. House races in the state and year that were won by 10% or less.
% 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

Competitiveness in ; state legislatures
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State Senate competitiveness, Colorado
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	35	51.4	33.3	0	0	16.7	0	11.1	75	66.7	62.5	100
1970	35	48.6	47.1	0	17.6	23.5	0	23.5	88.9	52.9	100	85.7
1972	35	51.4	27.8	0	11.1	22.2	0	22.2	92.3	72.2	100	88.9
1974	35	51.4	61.1	0	22.2	27.8	0	11.1	70	55.6	50	83.3
1976	35	51.4	38.9	0	11.1	22.2	0	22.2	100	50	100	100
1978	35	48.6	35.3	0	5.9	11.8	0	35.3	88.9	52.9	80	100
1980	35	51.4	38.9	0	5.6	11.1	0	27.8	100	72.2	100	100
1982	35	51.4	38.9	0	5.6	16.7	0	38.9	87.5	44.4	100	80
1984	35	54.3	21.1	0	5.3	10.5	0	52.6	100	57.9	100	100
1986	35	48.6	35.3	0	17.6	17.6	0	29.4	100	58.8	100	100
1988	35	54.3	26.3	0	5.3	21.1	0	31.6	100	52.6	100	100
1990	35	48.6	41.2	0	0	11.8	0	35.3	100	70.6	100	100
1992	35	51.4	50	0	11.1	27.8	0	33.3	83.3	66.7	100	77.8
1994	35	48.6	41.2	0	17.6	23.5	0	29.4	90.9	64.7	100	87.5
1996	35	54.3	47.4	0	21.1	26.3	0	31.6	88.9	47.4	66.7	100
1998	35	48.6	41.2	0	11.8	41.2	0	17.6	100	35.3	100	100
2000	35	54.3	57.9	0	21.1	42.1	0	5.3	83.3	31.6	100	66.7
2002	35	48.6	41.2	0	17.6	23.5	0	29.4	100	47.1	100	100
2004	35	51.4	61.1	0	11.1	16.7	0	16.7	90.9	61.1	100	80
2006	35	51.4	55.6	0	5.6	11.1	0	11.1	77.8	50	100	50
2008	35	54.3	68.4	0	10.5	26.3	0	10.5	100	42.1	100	100
2010	35	54.3	52.6	0	21.1	31.6	0	5.3	100	42.1	100	100
2012	35	57.1	65	0	10	30	0	0	100	45	100	100
2014	35	51.4	38.9	0	33.3	38.9	0	22.2	88.9	50	80	100

State House

State House competitiveness, Colorado
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	65	100	40	0	10.8	26.2	0	12.3	91.5	72.3	78.9	100
1970	65	100	41.5	0	13.8	33.8	0	15.4	93.9	75.4	94.1	93.8
1972	65	100	43.1	0	18.5	24.6	0	13.8	97.4	58.5	100	95.2
1974	65	100	60	0	20	36.9	0	10.8	81.8	67.7	90	78.3
1976	65	100	46.2	0	13.8	24.6	0	16.9	87	83.1	80.6	100
1978	65	100	43.1	0	1.5	15.4	0	27.7	93	66.2	94.1	92.3
1980	65	100	40	0	9.2	23.1	0	26.2	87.8	75.4	79.2	96
1982	65	100	38.5	0	16.9	23.1	0	30.8	90	61.5	92.9	88.5
1984	65	100	27.7	0	7.7	13.8	0	35.4	89.8	75.4	76.5	96.9
1986	65	100	38.5	0	13.8	20	0	26.2	85.7	75.4	92.3	83.3
1988	65	100	40	0	10.8	18.5	0	29.2	96.1	78.5	90.9	100
1990	65	100	40	0	10.8	21.5	0	24.6	89.3	86.2	87.5	90.6
1992	65	100	47.7	0	10.8	13.8	0	16.9	97.7	66.2	100	96.3
1994	65	100	36.9	0	7.7	16.9	0	20	88.7	81.5	79.2	96.6
1996	65	100	36.9	0	7.7	20	0	29.2	97.7	67.7	100	96.9
1998	65	100	38.5	0	10.8	20	0	23.1	100	61.5	100	100
2000	65	100	41.5	0	13.8	24.6	0	18.5	93	66.2	87.5	96.3
2002	65	100	43.1	0	20	29.2	0	24.6	93.9	75.4	90.5	96.4
2004	65	100	53.8	0	10.8	18.5	0	23.1	93.5	70.8	100	88
2006	65	100	60	0	7.7	18.5	0	23.1	92.5	61.5	100	76.9
2008	65	100	58.5	0	6.2	13.8	0	13.8	97.8	70.8	96.3	100
2010	65	100	49.2	0	12.3	20	0	16.9	87.2	72.3	81.5	100
2012	65	100	56.9	0	3.1	13.8	0	3.1	89.5	58.5	100	80
2014	65	100	52.3	0	10.8	27.7	0	20	93.6	72.3	90	100

Up ballot competitiveness, Colorado
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								22.5
1916								27.2
1920								24.6
1924								44.4
1928								31.2
1932								13.9
1936								23.9	11.1
1938									12.2
1940								2.6	9.5
1942						14.2	1.1		12.9
1944						12.8		6.8	4.8
1946	4	0	25	50	0				4.2
1948	4	0	75	75	0	34.7		5.4	32.7
1950	4	0	50	50	0	6.5			5.2
1952	4	0	50	50	0			21.5	14.7
1954	4	0	0	50	0	2.6			7.1
1956	4	0	25	50	0	0.4		20.9	2.7
1958	4	0	25	50	0				16.8
1960	4	0	25	25	0	7.5		9.8
1962	4	0	0	25	0	8.1			14.1
1964	4	0	50	50	0			23.2
1966	4	0	50	50	0	16.1			10.8
1968	4	0	50	75	0	17.1		10
1970	4	0	0	25	0				7.4
1972	5	0	40	40	0	1.1		28.8
1974	5	0	40	40	0	18.3			7.6
1976	5	0	40	60	0			11.9
1978	5	0	20	40	0	18.5			20.8
1980	5	0	0	0	0	1.7		27.9
1982	6	0	0	16.7	0				34.9
1984	6	0	0	16.7	16.7	30		28.7
1986	6	0	33.3	33.3	0	1.6			17.3
1988	6	0	0	0	0			7.9
1990	6	0	0	16.7	0	14.4			27.2
1992	6	0	0	0	0	9.6		5.6
1994	6	0	0	0	16.7				17.8
1996	6	0	0	0	0	5.1		1.5
1998	6	0	16.7	16.7	0	28.2			0.9
2000	6	0	0	0	33.3			9
2002	7	0	14.3	14.3	0	4.6			30.1
2004	7	0	14.3	28.6	0	4.9		4.7
2006	7	0	14.3	14.3	14.3				17.3
2008	7	0	0	0	0	10.8		9.1
2010	7	0	14.3	14.3	0	1.7			16.7
2012	7	0	14.3	14.3	14.3			5.5
2014	7	0	0	14.3	14.3	2.1			3.5

Click on a different state below for more detailed data on electoral competitiveness.