Policy Change and Public Opinion: Measuring Shifting Political Sentiment With Social Media Data

Date01 September 2020
Published date01 September 2020
Subject MatterArticles
American Politics Research
2020, Vol. 48(5) 612 –621
© The Author(s) 2020
Article reuse guidelines:
DOI: 10.1177/1532673X20920263
Researchers are divided over how the Supreme Court
impacts American public opinion. One group of scholars
argues that the public moves with the Justices’ rulings, gar-
nering consensus through strength of argument and the
legitimacy of the courts (Lerner, 1967). Another camp
argues that the public becomes further polarized after ruling
on a divisive issue, with those inclined to agree with the
Justices becoming more adamant in their support and those
predisposed to disagreement becoming further entrenched
in their opposition (Franklin & Kosaki, 1989). While these
studies consider the ways in which public opinion changes
temporally in the wake of a Supreme Court decision, few
analyze the state-by-state reactions to federal rulings, criti-
cal if a decision aligns with one state’s existing legal frame-
work but overturns another’s. This article extends previous
research into Supreme Court rulings and public opinion by
incorporating a state-level analysis in studying the Obergefell
v. Hodges decision and the federal legalization of same-sex
marriage in the United States.
In June of 2015 in a 5-4 ruling, the Supreme Court held
that the right to marry was a “fundamental right” under the
Due Process Clause of the Fourteenth Amendment, instanta-
neously overturning same-sex marriage bans in 13 states.1
This decision represents the most recent in a long line of
monumental cases in which the Court made a ruling on a
divisive social issue. Exploiting this variation in state laws
regarding the legality of same-sex marriage, I use a differ-
ence-in-difference estimator to identify the causal impact of
a policy change on the expression of sentiment toward same-
sex marriage.2 I find this impact to be negative, indicating a
less positive response by those in the affected states, even
when controlling for potentially relevant demographic vari-
ables and party identification.
While many studies use polling or survey data to measure
the shift in public opinion before and after landmark deci-
sions (e.g., Christenson & Glick, 2015; Franklin & Kosaki,
1989; Hanley et al., 2012; Johnson & Martin, 1998), this
article uniquely investigates these issues by using a subset of
Twitter messages regarding same-sex marriage and gay
rights issues. By implementing machine-learning methodol-
ogies to extract measures of sentiment from a large collec-
tion of tweets before and after the Supreme Court decision, I
analyze a finely grained data set that allows for new insights
into the short-term dynamics between Supreme Court
decisions and public opinion. Studying this relationship is
920263APRXXX10.1177/1532673X20920263American Politics ResearchAdams-Cohen
1California Institute of Technology, Pasadena, USA
Corresponding Author:
Nicholas Joseph Adams-Cohen, California Institute of Technology, 1200
East California Boulevard, Pasadena, CA 91125, USA.
Email: nadamsco@stanford.edu
Policy Change and Public Opinion:
Measuring Shifting Political Sentiment
With Social Media Data
Nicholas Joseph Adams-Cohen1
This article uses Twitter data and machine-learning methods to analyze the causal impact of the Supreme Court’s legalization
of same-sex marriage at the federal level in the United States on political sentiment and discourse toward gay rights. In
relying on social media text data, this project constructs a large data set of expressed political opinions in the short time
frame before and after the Obergefell v. Hodges decision. Due to the variation in state laws regarding the legality of same-
sex marriage prior to the Supreme Court’s decision, I use a difference-in-difference estimator to show that, in those states
where the Court’s ruling produced a policy change, there was relatively more negative movement in public opinion toward
same-sex marriage and gay rights issues as compared with other states. This confirms previous studies that show Supreme
Court decisions polarize public opinion in the short term, extends previous results by demonstrating opinion becomes
relatively more negative in states where policy is overturned, and demonstrates how to use social media data to engage in
causal analyses.
public opinion, political communication, text analysis, sentiment analysis, supreme court

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