Final answer:
The student's inquiry pertains to the historical increase in party unity and polarization in U.S. politics, especially after 1990, with consequences for government effectiveness and ideological division.
Step-by-step explanation:
The student's question seems concerned with the phenomenon of party unity and its historical peak in the year 2010, as well as the concept of polarization in American politics. In the decades after 1990, the trend in U.S. politics has been an increase in party unity and polarization. Unlike earlier decades, which saw a high level of bipartisanship and the election of many moderate politicians, the recent decades have witnessed the parties diverging, with fewer moderates and more ideologically extreme politicians. This shift has had significant implications for the functioning of the U.S. government, including a decrease in legislative productivity and an increase in national issues driving congressional elections.
Historically, parties were more willing to work together, resulting in legislation with broad support and a range of ideologies within each party. However, starting in the 1990s, there was a marked change in this trend as partisan division deepened, indicated by ideological homogenization within parties and an increase in straight-ticket voting. This polarization has had several effects, including distinct choices for voters, but also a decrease in government effectiveness. For example, congressional productivity in terms of substantive legislation has declined, as shown by the comparison of the 106th and 113th Congress.