1 Items: System Justification

Items confirmed as identical across all included waves (2016, 2018, 2020).

2 Study Overview

Sample sizes and descriptive statistics for System Justification by year
year	N	N (valid facet)	Mean	SD
2016	1500	1500	5.06	1.32
2018	2759	2759	5.05	1.51
2020	2000	2000	4.91	1.65

2.0.1 2016 Sample

2.0.2 Sample

N=1500

To conduct a exploratory and a confirmatory large surveys during the general election, we hired a professional survey firm (SSI, a US-based market research company that recruits participants from a panel of 7,139,027 American citizens; more information can be found at www.surveysampling.com (now https://www.dynata.com/) to recruit a nationally representative sample of 1,500 Americans (50.7% women) who completed study materials during the general election from August 16-September 9, 2016. (Information about sampling and exclusion criteria is included in the Supplement). The age distribution was as follows: 18-24 (12.9%), 25-34 (17.6%), 35-44 (17.5%), 45-54 (19.5%), 55-65 (15.6%) and older than 65 (16.9%). The ethnic breakdown was: White/European American (82.5%), Black/African American (7.7%), Latino (5.9%) and “Other” (4.0%). Concerning religion, 67.6% identified as Christian, 17.1% as religiously affiliated but not Christian, and 15.3% as Atheist/Agnostic. With respect to education 35.1% indicated “high school only or lower,” 31.4 % indicated “some college,” and 33.6% indicated having received a “Bachelor” or “Graduate” degree. 2424 participants were directed to the survey, 1885 of which finished the survey (attrition rate 22%).

We followed recommendations to minimize the problem of careless responding in online studies. Specifically, we employed 10 random attention questions and time controls to check for data quality. There were 385 participants who failed more than one attention check or finished the survey in under ~22 minutes and were therefore excluded from the sample. For the 1500 participants who successfully finished the survey, completion time was 67 minutes on average (MD: 51min).

2.0.3 2018 Sample

2.0.4 Sample

N=TBD

Sample description for the 2018 PPBS CINT Post-election study to be added.

2.0.5 2020 Sample

2.0.6 Sample

N=TBD

Sample description for the 2020 PPBS CINT study to be added.

3 Descriptives

Descriptive statistics for System Justification by year
year	N	Mean	SD	Median	Min	Max	Skewness	Kurtosis
2016	1500	5.06	1.32	5.12	1	8.62	-0.24	0.00
2018	2759	5.05	1.51	5.12	1	9.00	-0.24	-0.14
2020	2000	4.91	1.65	5.00	1	9.00	-0.28	-0.42

4 Demographics

4.1 Sex

4.1.1 Pooled Model with Year Interaction

System Justification ~ Sex * Year
	System Justification
Predictors	Estimates	CI	p
(Intercept)	4.81	4.70 – 4.91	<.001
Sex [Male]	0.51	0.36 – 0.66	<.001
year [2018]	0.11	-0.02 – 0.25	.100
year [2020]	-0.09	-0.23 – 0.05	.198
Sex [Male] × year [2018]	-0.24	-0.43 – -0.05	.012
Sex [Male] × year [2020]	-0.10	-0.30 – 0.10	.315
Observations	6259
R² / R² adjusted	.018 / .017

4.1.2 Raincloud by Year

4.2 Age

4.2.1 Pooled Model with Year Interaction

System Justification ~ Age * Year
	System Justification
Predictors	Estimates	CI	p
(Intercept)	4.70	4.49 – 4.90	<.001
Age25-34 years	-0.11	-0.38 – 0.16	.426
Age35-44 years	0.27	-0.00 – 0.54	.053
Age45-54 years	0.30	0.04 – 0.57	.025
Age55-64 years	0.73	0.46 – 1.01	<.001
Age [65+]	0.96	0.69 – 1.23	<.001
Age [65+ years]	1.50	1.27 – 1.73	<.001
year [2018]	-0.39	-0.65 – -0.12	.004
year [2020]	-0.72	-1.00 – -0.44	<.001
Age25-34 years:year2018	0.41	0.07 – 0.75	.019
Age35-44 years:year2018	0.29	-0.05 – 0.64	.096
Age45-54 years:year2018	0.53	0.20 – 0.87	.002
Age55-64 years:year2018	0.31	-0.04 – 0.65	.085
Age [65+ years] × year [2018]	-0.19	-0.50 – 0.12	.237
Age25-34 years:year2020	0.52	0.16 – 0.88	.004
Age35-44 years:year2020	0.63	0.26 – 0.99	.001
Age45-54 years:year2020	0.69	0.33 – 1.05	<.001
Age55-64 years:year2020	0.71	0.34 – 1.07	<.001
Observations	6259
R² / R² adjusted	.088 / .086

4.2.2 Raincloud by Year

4.3 Income

4.3.1 Pooled Model with Year Interaction

System Justification ~ Income * Year
	System Justification
Predictors	Estimates	CI	p
(Intercept)	4.71	4.49 – 4.93	<.001
Income [$15,000-$24,999]	0.05	-0.26 – 0.36	.771
Income [$25,000-$34,999]	0.28	-0.03 – 0.59	.079
Income [$35,000-$49,999]	0.20	-0.10 – 0.49	.186
Income [$50,000-$74,999]	0.33	0.05 – 0.61	.021
Income [$75,000-$99,999]	0.55	0.24 – 0.86	<.001
Income [$100,000-$149,999]	0.84	0.52 – 1.16	<.001
Income [$150,000 +]	0.88	0.51 – 1.26	<.001
year [2018]	-0.09	-0.36 – 0.19	.540
year [2020]	-0.04	-0.33 – 0.26	.802
Income [$15,000-$24,999] × year [2018]	0.10	-0.29 – 0.50	.604
Income [$25,000-$34,999] × year [2018]	-0.08	-0.48 – 0.32	.709
Income [$35,000-$49,999] × year [2018]	0.29	-0.08 – 0.66	.128
Income [$50,000-$74,999] × year [2018]	0.29	-0.06 – 0.64	.106
Income [$75,000-$99,999] × year [2018]	-0.01	-0.39 – 0.38	.974
Income [$100,000-$149,999] × year [2018]	-0.38	-0.78 – 0.01	.055
Income [$150,000 +] × year [2018]	-0.14	-0.58 – 0.30	.524
Income [$15,000-$24,999] × year [2020]	0.10	-0.33 – 0.52	.661
Income [$25,000-$34,999] × year [2020]	-0.15	-0.58 – 0.28	.494
Income [$35,000-$49,999] × year [2020]	-0.02	-0.41 – 0.38	.939
Income [$50,000-$74,999] × year [2020]	-0.12	-0.49 – 0.26	.544
Income [$75,000-$99,999] × year [2020]	-0.15	-0.56 – 0.26	.461
Income [$100,000-$149,999] × year [2020]	-0.50	-0.92 – -0.09	.017
Income [$150,000 +] × year [2020]	-0.44	-0.91 – 0.02	.059
Observations	6259
R² / R² adjusted	.023 / .019

4.4 Ethnicity

4.4.1 Pooled Model with Year Interaction

System Justification ~ Ethnicity * Year
	System Justification
Predictors	Estimates	CI	p
(Intercept)	5.11	5.02 – 5.19	<.001
Ethnicity [Black/African American]	-0.50	-0.79 – -0.22	.001
Ethnicity [Latino]	0.09	-0.24 – 0.41	.605
Ethnicity [Asian/Pacific Islander]	-0.19	-0.74 – 0.36	.491
Ethnicity [Native American]	-0.40	-1.22 – 0.41	.330
Ethnicity [Other]	-0.55	-1.24 – 0.14	.119
Ethnicity [White]	-0.32	-1.22 – 0.57	.481
Ethnicity [Hispanic/Latino]	-1.00	-1.95 – -0.06	.037
Ethnicity [Middle Eastern]	-0.17	-1.71 – 1.37	.825
Ethnicity [Middle Eastern]	-2.85	-5.10 – -0.61	.013
year [2018]	0.61	-0.36 – 1.58	.220
year [2020]	0.31	-0.58 – 1.20	.494
Ethnicity [Black/African American] × year [2018]	-0.65	-1.67 – 0.37	.212
Ethnicity [Asian/Pacific Islander] × year [2018]	-0.49	-1.65 – 0.66	.403
Ethnicity [Native American] × year [2018]	-0.61	-2.09 – 0.88	.425
Ethnicity [Other] × year [2018]	-1.45	-2.30 – -0.60	.001
Ethnicity [White] × year [2018]	-0.17	-0.58 – 0.24	.426
Ethnicity [Black/African American] × year [2020]	-0.72	-1.66 – 0.23	.138
Ethnicity [Asian/Pacific Islander] × year [2020]	-0.66	-1.74 – 0.42	.230
Ethnicity [Native American] × year [2020]	-0.87	-2.32 – 0.58	.240
Observations	6259
R² / R² adjusted	.039 / .036

4.5 Area

4.5.1 Pooled Model with Year Interaction

System Justification ~ Area * Year
	System Justification
Predictors	Estimates	CI	p
(Intercept)	5.07	4.97 – 5.16	<.001
Area [Rural]	-0.02	-0.18 – 0.14	.810
Area [Suburban]	0.39	0.23 – 0.54	<.001
year [2018]	-0.18	-0.33 – -0.03	.015
year [2020]	-0.46	-0.61 – -0.30	<.001
Area [Rural] × year [2018]	0.21	-0.01 – 0.44	.062
Area [Suburban] × year [2018]	-0.14	-0.35 – 0.06	.170
Area [Rural] × year [2020]	0.52	0.27 – 0.77	<.001
Observations	6259
R² / R² adjusted	.009 / .008

5 Political Orientation

5.1 Fixed-Effects Regression: Ideology ~ Construct * Year

5.1.1 Regression Table

	System Justification → Ideology (Pooled)			System Justification → Ideology (2016)			System Justification → Ideology (2018)			System Justification → Ideology (2020)
Predictors	Estimates	CI	p	Estimates	CI	p	Estimates	CI	p	Estimates	CI	p
(Intercept)	6.01	0.93 – 11.09	.021	4.20	3.59 – 4.80	<.001	16.41	11.36 – 21.47	<.001	5.34	0.42 – 10.27	.034
facet	0.17	-0.75 – 1.09	.725	0.16	0.06 – 0.25	.001	6.96	6.25 – 7.68	<.001	10.13	9.42 – 10.84	<.001
year [2018]	10.12	4.52 – 15.72	<.001
year [2020]	-2.71	-8.45 – 3.03	.355
Age25-34 years	1.23	-0.98 – 3.44	.274	-0.18	-0.62 – 0.27	.435	0.31	-3.70 – 4.32	.880	3.38	-0.85 – 7.62	.118
Age35-44 years	1.58	-0.69 – 3.84	.173	0.12	-0.34 – 0.57	.621	2.82	-1.30 – 6.93	.180	0.34	-4.01 – 4.69	.879
Age45-54 years	4.42	2.17 – 6.66	<.001	0.43	-0.02 – 0.87	.058	6.36	2.25 – 10.46	.002	5.07	0.72 – 9.42	.022
Age55-64 years	3.24	0.94 – 5.54	.006	0.60	0.13 – 1.07	.012	5.83	1.69 – 9.97	.006	1.62	-2.81 – 6.05	.473
Age [65+]	3.75	0.14 – 7.35	.042	1.60	1.14 – 2.06	<.001
Age [65+ years]	1.12	-1.26 – 3.50	.355				3.51	-0.53 – 7.55	.088	-0.10	-4.38 – 4.19	.965
Inc	0.18	-0.12 – 0.48	.231	0.08	0.01 – 0.15	.027	0.92	0.41 – 1.43	<.001	-0.69	-1.26 – -0.13	.016
Edu	-1.56	-2.23 – -0.90	<.001	-0.15	-0.27 – -0.02	.027	-2.74	-3.86 – -1.61	<.001	-0.96	-2.46 – 0.54	.210
facet × year [2018]	7.15	6.06 – 8.23	<.001
facet × year [2020]	9.73	8.63 – 10.84	<.001
Observations	6259			1500			2759			2000
R² / R² adjusted	.497 / .496			.080 / .076			.154 / .152			.303 / .300

5.1.2 Scatter Plots by Year

5.1.3 Forest Plot: Meta-Analytic Pooling

5.2 Social Ideology

	Social Ideology (Pooled)			Social Ideology (2016)			Social Ideology (2018)			Social Ideology (2020)
Predictors	Estimates	CI	p	Estimates	CI	p	Estimates	CI	p	Estimates	CI	p
(Intercept)	3.77	-1.29 – 8.83	.144	3.77	3.22 – 4.32	<.001	11.18	7.25 – 15.10	<.001	-0.32	-4.07 – 3.43	.868
facet	0.23	-0.74 – 1.20	.643	0.23	0.12 – 0.33	<.001	7.51	6.77 – 8.26	<.001	10.25	9.53 – 10.97	<.001
year [2018]	7.41	1.37 – 13.45	.016
year [2020]	-4.09	-10.22 – 2.05	.192
facet × year [2018]	7.28	6.13 – 8.44	<.001
facet × year [2020]	10.02	8.84 – 11.20	<.001
Observations	6259			1500			2759			2000
R² / R² adjusted	.445 / .444			.012 / .011			.124 / .124			.279 / .278

5.3 Economic Ideology

	Economic Ideology (Pooled)			Economic Ideology (2016)			Economic Ideology (2018)			Economic Ideology (2020)
Predictors	Estimates	CI	p	Estimates	CI	p	Estimates	CI	p	Estimates	CI	p
(Intercept)	3.74	-1.06 – 8.54	.127	3.74	3.22 – 4.25	<.001	15.56	11.84 – 19.27	<.001	1.30	-2.26 – 4.87	.474
facet	0.34	-0.57 – 1.26	.462	0.34	0.25 – 0.44	<.001	7.62	6.92 – 8.33	<.001	10.81	10.12 – 11.49	<.001
year [2018]	11.82	6.10 – 17.55	<.001
year [2020]	-2.43	-8.25 – 3.39	.413
facet × year [2018]	7.28	6.18 – 8.37	<.001
facet × year [2020]	10.46	9.34 – 11.58	<.001
Observations	6259			1500			2759			2000
R² / R² adjusted	.508 / .508			.030 / .029			.140 / .140			.322 / .322

6 Party Identity Analyses

6.1 Party Identity (7-Point ANES) by Year

6.2 Party Identity Raincloud

6.3 Party Identity Regression with Year Interaction

	Party ID (Pooled)			Party ID (2016)			Party ID (2018)			Party ID (2020)
Predictors	Estimates	CI	p	Estimates	CI	p	Estimates	CI	p	Estimates	CI	p
(Intercept)	1.26	1.16 – 1.35	<.001	1.26	1.16 – 1.35	<.001	0.85	0.79 – 0.91	<.001	0.74	0.68 – 0.80	<.001
facet	0.05	0.03 – 0.07	<.001	0.05	0.03 – 0.07	<.001	0.12	0.10 – 0.13	<.001	0.15	0.14 – 0.16	<.001
year [2018]	-0.40	-0.51 – -0.29	<.001
year [2020]	-0.52	-0.63 – -0.41	<.001
facet × year [2018]	0.07	0.05 – 0.09	<.001
facet × year [2020]	0.10	0.08 – 0.12	<.001
Observations	6259			1500			2759			2000
R² / R² adjusted	.139 / .138			.017 / .016			.123 / .123			.245 / .244

6.4 Forest Plot: Party ID Regression

7 Correlation Comparison

7.1 Cleveland Dot Plot: Correlations by Year

7.2 Forest Plots: Key Correlations

7.2.2 Economic System Justification

7.2.3 Ideological Self-placement [Economic]

7.2.4 Ideological Self-placement [Left-Right]

7.2.5 Right Wing Authoritarianism

7.2.6 Party ID [G.O.P.]

7.3 Correlation Table by Year

Spearman correlations with System Justification by year
label	2016	2018	2020
Age	0.273	0.290	0.299
Anti-Pluralism [Populist Attitudes]	-0.037	0.019	0.095
Blind Patriotism	-0.326	0.575	0.557
Economic System Justification	0.335	0.491	0.623
Education	0.124	0.008	0.082
Ideological Self-placement [Economic]	0.167	0.370	0.561
Ideological Self-placement [Left-Right]	0.148	0.379	0.547
Ideological Self-placement [Social]	0.102	0.349	0.527
Income	0.208	0.129	0.088
Male	0.190	0.092	0.122
Party ID [G.O.P.]	0.127	0.359	0.508
Religiosity	0.114	0.251	0.340
Right Wing Authoritarianism	0.081	0.382	0.533
Rural Area	-0.012	0.056	0.104
Social Dominance Orientation	0.134	0.320	0.455
Support for Black Lives Matter	-0.079	-0.278	-0.529
Support for Blue Lives Matter	0.174	0.285	0.420
Support for Civil Rights	-0.046	-0.183	-0.328
Support for Environmentalism	-0.054	-0.246	-0.360
Support for Feminism	-0.017	-0.217	-0.339
Support for LGBTQ+	-0.092	-0.280	-0.436