It’s Party Time!
Visualizing the evolution of the US political party system through the Senate.
Fall 2020
With today’s swirling headlines about party polarization and unprecedented attention on Georgia’s runoff race for control of the Senate, I decided to rewind it back a couple hundred years to look at the history of party control in the Senate.
The Most Seats at the Table
The visual below shows party magnitude in terms of Senator-years* (the sum of the number of years in which a Senator from that party served) from the formation of the Senate in 1789 to 2020. Unsurprisingly, an overwhelming majority of the area is dominated by the Democratic Party and the Republican Party. They’re not only the two parties that dominate the political landscape today but have also existed for close to 150 years, though the ideologies each party has stood for has shifted quite a bit.
Other relatively larger parties include the Democratic-Republicans, Whigs, and Federalists, which existed during the early years of the country. Investigate the graph and take a chance to explore some of the lesser-known parties and their relationships. For example, the Silver Republicans broke off from the main party at the turn of the 20th century for the single issue of expansionary monetary policy in the form of free silver. Though the Unionists and the Unconditional Unionists both sprang up around the time of the Civil War to oppose secession, the Unconditional Unionists organized in the border states, as opposed to the North where the Unionists resided and made an effort to quell anti-Union sentiment among some states considering secession.
* I used Senator-years over a count of Senator terms since there were many cases in which a Senator did not serve their full term (for reasons that will be covered later in the project), so this count is more accurate.
Serving Their Time
I also wanted to explore the overall tenure that Senators serve. Unsurprisingly, we see that there is a clear spike in the graph every 6 years, representing the normal term length. However, some Senators leave their post in the middle for a variety of reasons, often to serve in the executive branch, such as Obama did in 2008 and Harris will do for her Vice Presidency. This graph also has a long right tail, pointing to the several Senators that have served many decades on Capitol Hill. Notable highlights include Joe Biden and Mitch McConnell who have both held their seats for 36 years.
Here we can see that average tenure also varies widely between different parties. This could point to a larger difference among the “lifespans” of different political movements. Many smaller parties merged focused on a single issue and dissolved once these points were resolved or dismissed with their respective Senators often rejoining a majority party.
On the topic of tenure, there seems to be an increasing trend toward tenure length as the years go by. Looking at the graph above, we see that the pale purple portion of the graph has been increasing, especially over the past centory. This means that more of our current Senate is composed of veteran Senators, people who have held their seats for over 12 years when compared with before. This can be concerning or comforting depending on your viewpoint since longer-serving Senators can be seen as more experienced and are expected to represent their constituents well to be re-elected. On the other hand, this stagnation in turnover could also lead to complacency as well as a lack of new viewpoints as their long terms are fueled by inertia rather than fresh ideas. Currently, the average term experience for the 117th Senate is 11 years with the median age being 67 years. This number seems quite large (and past the average age of retirement), however, taking into account that some Senators have served multiple terms, we can look to the median age that these Senators took office, which is 51 years (younger, but only relatively).
It also found it enlightening to read up on the history of careers on Capitol Hill. Contrary to what we see today, many lawmakers in the 18th and early 19th centuries were actually “citizen legislators,” meaning that they held other full-time employment and served in Congress on a part-time basis for a short number of years. The high turnover and a lack of seniority structure likely contributed to shorter terms we see for the early years. A turning point came after the Civil War, as new structures were implemented that contributed to the rise of careerism in Congress.
If you want to learn more about the history of service tenures in Congress and explore some visualizations on reelection rates and cross-chamber experience, check out the Congressional Research Service’s report.
Trends Over Time
This graph shows the summation of Senators for each decade with each color representing a different party. You can really start seeing the rise and fall of different political party systems and major events. For example, the height of the bar grows somewhat steadily for the first 150 years since the number of Senators increase as more states are added to the US. You also might notice the dip in the 1860s, an indication of the Southern states that seceded from the Union during the Civil War and were consequently no longer sending Senators to Washington.
Party-wise, one of the most notable turning points is in the mid-1800s as the Era of Good Feelings saw the end of the nation’s first party system between Federalists (green) and Democratic-Republicans (orange). This was due to the Federalist’s refusal to support the War of 1812 that dramatically decreased party support. So the Presidency of James Monroe (1816-1824) saw little partisanship and was aptly named the Era of Good Feelings.
This graph can also be viewed in terms of percent totals to get a better sense of which party held majority control in the given decades.
To make it more familiar, we can look at the Senate distribution for the past 10 years to see how majorities have narrowed. In addition, it’s important to tie-in this data with the larger political context. In 2016, not only was there a Republican majority in the Senate, but they also held the House and the Presidency.
Map it Out!
Finally, we can map the states geographically and animate them across the years. Jump to a specific year on the graph below or simply press play and watch the states animate as Senators of different parties represent them throughout the years.
Starting with the first party system of the Federalists versus the Democratic-Republicans, then onto the rise of Whigs and Democrats as states are added one-by-one. As tensions on the issue of slavery grow, Missouri and California receive statehood through the Missouri Compromise and the Compromise of 1850, respectively. At the end of 1860, South Carolina secedes from the Union with the other southern states quickly follow suit. After the Civil War, we see the Southern states beginning with Union-friendly Republican Senators that slowly shifted to the Democrats as Reconstruction came to a close. I was surprised to see that even as recent as the 1990s, the geographical spread of the parties in the Senate was contrary to my expectations, with the South being made up entirely of blue and purple states.
This animation is one of those in which you notice something new with every re-watch, so play it back a couple more times and see what you can discover!
What’s Next?
Though this project has given me much insight into the different political parties in the Senate (and also some unfortunate flashbacks to my high school history class), the Senate is only one piece of the larger political system. I would love to investigate deeper on how party control in the Senate was reflected in or conflicted with majority party of the House or Presidency. Doing further research on the impact of divided presidencies or split Congresses will give me a greater understanding of policy compromise, gridlock, and gerrymandering.
