If you ask members of the US Senate they serve as members of the “world’s greatest deliberative body.” Such a reputation, if well-deserved, would uniquely position them to serve as jurors for the impeachment trial of a President of the United States. Outside of the US Senate there is a different opinion, especially among those who want to see President Donald Trump removed from office. Rather than ideal jurors they see US Senators as partisan hacks whose minds were made up long before hearing even the first word of an opening statement.
But what makes jurors, or a jury, good at deciding cases? Historically one approach to answering this question comes from the work of 18th-century French philosopher Marie-Jean-Antoine-Nicolas de Caritat, the Marquis of Condorcet. His work involved the application of mathematical methods to solving economical, political, and social problems. Condorcet is perhaps most well-known for a theory about group decision making that now bears his name, the Condorcet Jury Theorem. Briefly the theory says that given independent jurors, each with a better than 50% chance to determine the correct answer to a factual question, each juror added to the pool increases the chances that the jury will collectively arrive at the correct answer to a factual question. Here being independent means that each juror comes to a conclusion about the question based on their own reasoning and understanding, rather than deferring to someone else’s decision. Hence, in theory, with enough such jurors it is guaranteed that the correct answer will be reached. With this principle in mind it’s possible for us to get an idea of what might, in theory, make the US Senate a good jury. Then we can see how, in practice, Senators might fail to live up to their vaunted reputation.
The endless refrain of Senate cheerleaders is a familiar civics lesson. Senators act as trustees of their states while House members act as delegates. Whereas delegates, in theory, act directly on the impetus of their constituents’ wishes, trustees act on their own judgment and understanding. Hence, the Senate is an experienced and independent deliberative body by design. Its superior experience is supposed to be a factor of the higher age limit imposed on potential Senators. Whereas a member of the House of Representatives must only be older than 25, a member of the Senate must be older than 30. Further Senators were originally chosen not by popular vote but by the legislatures of the state they represent. These state-level legislators were thought to be better able to select people of skill and influence than regular citizens, who in turn selected the state-level legislators for being more skilled and influential than they the voters are themselves. This more indirect election is also taken to be one of the factors that makes the Senators more independent. Because they are not beholden to the vicissitudes of popular opinion, and instead more attuned to the real needs of the Union, Senators are more fit to act as the upper house of the US Congress. Another factor meant to make them more independent is their term of office, which is six years rather than the two-year terms of members of the House of Representatives.
How does this turn out in practice? First, it is important to note that one of the features supposed to make Senators more like trustees than delegates has been altered since the drafting of the US Constitution. As of the 17th Amendment to the US Constitution passed in 1913, US Senators are elected by popular vote in the states they represent. Senators are thus insulated from popular opinion only by their longer term of office. More relevant to the poor opinion of the Senate’s independence pertains to party polarization. The impeachment of President Donald Trump has, for the most part, neatly split along party lines: Democrats are in favor of removing Trump from office and have to persuade Republicans to their side. The members of the House, bringing articles of impeachment against Trump, built their opening arguments around the assumption of such partisanship. The lead House manager, Rep. Adam Schiff, even suggested that Senate Republicans closed their minds to any arguments for fear of their political future saying that Trump would have their “heads on a pike” if they turned on him.
The other issue is whether Senators are experienced in the right way to give them each a better than 50% chance to get the correct answer to the impeachment questions. There are two sets of questions at issue. First, did President Trump actually do the things of which he is accused: namely, abuse his power by making foreign aid dependent on political favors to him and obstruct Congress by completely refusing to recognize any subpoenas? Second, if President Trump did these things, do they constitute conduct for which he can be removed from office? The first set of questions is a matter of hearing testimony and receiving documents. However, the second question is a matter of Constitutional law. Broken down by profession, around half of the Senate comes from the legal profession and/or a public service and policy background. Hence there is at least some reason to think that the many Senators would be slightly better than chance at determining the correct answer to these questions of Constitutional law.
President Donald Trump’s impeachment trial is widely expected to result in his acquittal on both articles of impeachment. The belief that this result will not be based on a sound deliberative process can be seen as a belief that Senators largely fail to be independent decision-makers. Instead of basing their decisions on their own understanding of the facts at issue it is likely they are basing their decisions on the whip of Senate Majority Leader Mitch McConnell, the political influence of President Trump, and their re-election prospects based on the opinions of their constituents. So much for being the world’s greatest deliberative body.