With the second impeachment of Donald Trump, we can say that one piece of good news is that Samuels and Shugart (2010) are still right. In our book, Presidents, Parties, and Prime Ministers, one of our claims is that parties in presidential systems face a severe dilemma: On the one hand, they need leaders who can win a separate popular election. On the other hand, the leaders selected for that purpose may not always share the goals of the party, but the party is basically stuck with the president, given the fixed term. While impeachment and removal are usually available under constitutional provisions, it is almost an iron law that parties do not vote to impeach their own president.
On 13 January, and in the wake of the insurrection of 6 Jan., this theory was put to a severe stress test. In fact, the day before the impeachment vote, it looked like the dam had broken and there would be many defectors from the Republican Party, who would join with Democrats and vote to impeach. The biggest blow was Liz Cheney, with the no. 3 position in the GOP House leadership, announcing she would vote to impeach. That seemed like it could give cover to others who wanted to break with the president after his reprehensible actions the week before. The New York Times reported that Kevin McCarthy, the minority leader, “and other party leaders have decided not to formally lobby Republicans to vote “no”.” Moreover, according to the same report, the Republican Senate leader, Mitch McConnell believed Trump had committed impeachable offenses.
Yet, in the end, there were only ten defectors. While this is the highest number of Representatives from a president’s own party to have joined an impeachment vote in US history (all four such votes), it is only about 5% of the total number of party members in the House. Normally, we would think of 95% unity as pretty high, and thus the case of Trump’s impeachment conforms, so far, to the theory: the president’s party does not vote in favor of a process that could lead to removal of its own leader, the president.
By contrast, the book shows that for about a third of prime ministers in parliamentary systems the manner in which they leave office is due to their own party replacing them between elections. Fundamentally, prime ministers do not have fixed terms and are agents of their own parties. Presidents, on the other hand, typically cease to be agents of their parties upon being nominated and especially upon winning the presidential election. This is the key argument of the book: “Presidentialization” effectively reverses the principal–agent relationship, as party members have strong electoral and other incentives to follow the lead of the president whose term does not depend on their ongoing support.
Presidents’ parties may not always support the president’s legislative initiatives (although in most cases, they follow the big ones, even when such initiatives deviate from normal party priorities–see Chapter 8 of the book), but they do usually hold the ranks together when it comes to a co-partisan president’s continued tenure in office. Apparently, even after incitement to insurrection over refusal to accept a lost reelection bid, and even with only a week to go in the term.
In connection with the above argument, some have asked what about Richard Nixon? Had he not resigned, it would have been a bipartisan impeachment and removal. This is probably correct. We also have other cases in our dataset of presidents who resigned for one reason or another. Obviously, in these cases, we are unable to observe an impeachment vote, so they are outside our theory. We can thank Nixon and others for sparing their parties the need to violate an iron law!
More seriously, there is probably, theoretically, some floor of presidential approval below which the dynamic changes. I do not claim to know where that floor is, but Nixon probably breached it when his approval hovered near 20% at the end. Given the small N problem, this remains entirely speculative. The logic might be something about tipping points of support in the party member’s own constituencies, as opposed to a parliamentary party, which typically has a more collective leadership that looks out for swing voters who determine its ability to retain executive control in future elections. And in multiparty systems, this modelling would get even more complex. Lots of PMs lose office due to coalition collapse. Presidents rarely go out that way. There is the case of Dilma Rousseff in Brazil (2016), but it conforms to the theory: her party voted 0-10 in the Senate against conviction. Ultimately, her problem was that her party had only 10 of the 81 seats! (They had also voted 0-60 against impeachment in the Chamber of 513 total members.) There was also the case of Park Geun-hye in South Korea in 2016, where some unknown number of members of her party may have voted to impeach. The reason it is unknown is the vote is secret. If the logic of members not dumping a co-partisan president is tied to electoral incentives (fates of legislators tied to that of the president), then a secret vote would break that. In the book we also mention the case of Raúl Cubas Grau in Paraguay (1999), forced out during an impeachment vote by his own Colorado Party. In this case, the party held a super-majority, and could do it alone without fear of electoral blowback. We discuss some other cases with splits in a party. The bottom line is that there is nothing routine about impeachment, and the calculation of president’s co-partisans is usually that it is unwise to break with the leader who won your own voters’ support in the most recent election. Trump’s case would be the only one I am aware of in which the most recent presidential election was one he had lost, but we still saw a very high degree of overlap between vote for House GOP winners and votes for the president, meaning that a break is essentially saying to voters, sorry, you voted for a crook, so let us set things straight for you.
So 13 January may not have been a good day for American democracy, but it was a good day for comparative institutional political science.