  Estimating political positions of lawmakers has a long tradition in political
science. We present the time varying text based ideal point model to study the
political positions of lawmakers based on text data. In addition to identifying
political positions, our model also provides insights into topical contents and
their change over time. We use our model to analyze speeches given in the U.S.
Senate between 1981 and 2017 and demonstrate how the results allow to conclude
that partisanship between Republicans and Democrats increased in recent years.
Further we investigate the political positions of speakers over time as well as
at a specific point in time to identify speakers which are positioned at the
extremes of their political party based on their speeches. The topics extracted
are inspected to assess how their term compositions differ in dependence of the
political position as well as how these term compositions change over time.
