  Social media has been an important tool in the expansion of the populist
message, and it is thought to have contributed to the electoral success of
populist parties in the past decade. This study compares how populist parties
advertised on Facebook during the 2019 European Parliamentary election. In
particular, we examine commonalities and differences in which audiences they
reach and on which issues they focus. By using data from Meta (previously
Facebook) Ad Library, we analyze 45k ad campaigns by 39 parties, both populist
and mainstream, in Germany, United Kingdom, Italy, Spain, and Poland. While
populist parties represent just over 20% of the total expenditure on political
ads, they account for 40% of the total impressions$\unicode{x2013}$most of
which from Eurosceptic and far-right parties$\unicode{x2013}$thus hinting at a
competitive advantage for populist parties on Facebook. We further find that
ads posted by populist parties are more likely to reach male audiences, and
sometimes much older ones. In terms of issues, populist politicians focus on
monetary policy, state bureaucracy and reforms, and security, while the focus
on EU and Brexit is on par with non-populist, mainstream parties. However,
issue preferences are largely country-specific, thus supporting the view in
political science that populism is a "thin ideology", that does not have a
universal, coherent policy agenda. This study illustrates the usefulness of
publicly available advertising data for monitoring the populist outreach to,
and engagement with, millions of potential voters, while outlining the
limitations of currently available data.
