I raised the question with Steven Levitsky, a political scientist at Harvard who wrote the book “How Democracies Die” with his government department colleague Daniel Ziblatt.

Levitsky, responding to my emailed query, wrote:

There may well be something to the claim that Trump’s is a disjunctive presidency representing the end of the Reagan era. But to jump from there to the conclusion that he does not pose a serious threat to democratic institutions strikes me as facile. Such a claim too easily sets aside important contextual differences between this administration and those of other “disjunctive” presidents.

Levitsky provided a long list of contemporary factors that distinguish the Trump presidency from the Hoover and Carter presidencies, including

extreme partisan polarization along overlapping social/cultural/cleavages, the hardening of partisan identities and the rise of intense negative partisanship, the crystallization of white identities and the perception among some white voters of threat in the face of decades of immigration and steps toward racial equality; dramatically higher levels of income inequality and declining social mobility; the weakening of party elites’ gatekeeping capacity, reinforced by the introduction of party primaries, and, in the context of extreme polarization, the erosion of key democratic norms.

Levitsky’s argument goes beyond the overarching political environment to Trump’s character.

Trump “has shown himself,” Levitsky continued,

to be a more openly autocratic figure than any of the other disjunctive president I am aware of. So we have a president with authoritarian instincts in a context of extreme partisan polarization (such that Republicans line up behind Trump no matter what) and weakened norms. That strikes me as quite a bit different — and more threatening — than say, the Carter presidency.

In addition, Trump must be viewed as the avatar not only of an American political phenomenon but a global one.

Levitsky argues that the “disjunctive presidency” theory

lacks any comparative or global perspective. There are changes occurring globally that have unleashed illiberal or populist right wing reactions across much of the industrialized West. Whether it is globalization, migration and ethnic diversification, technological change, or some combination thereof, at least some of the dynamics that are occurring in the US cannot be understood in a vacuum. It would therefore be silly to assume that the context in which we are operating in 2019 is easily comparable to those of 1924-28 or 1976-80.

Ziblatt, Levitsky’s co-author, argued in an email that it is a highly risky proposition to take any comfort in a theoretical construct placing Trump as the endpoint of the Reagan era:

It is very, very dangerous way to feel reassured and to write off the Trump presidency as the final, dying days of the Reagan era. There are certainly analogies to be drawn from earlier eras but it is only an analogy, not a law of history.

Trump stands apart from past presidents in his willingness to capitalize on what Ziblatt identifies as an “existential fear” among voters in the face of broad demographic change:

The huge demographic changes underway in the U.S. since the 1970s have prompted Republican existential fear about the future and an increasingly stiff resistance to democracy itself. Like Conservatives in Europe before 1914 or Southern Democrats in the 1890s, fear of the future means a greater willingness to play dirty and to block the emergence of any “recuperative presidency.”

Theda Skocpol, professor of government and sociology at Harvard, sharply criticized the Skowronek-Balkin theory because it masks what she contends is a fundamentally different and dangerous moment in American politics:

We are in a very extreme period in U.S. political history because of the radicalization of the GOP and the apparent willingness of virtually all of its officeholders, candidates, and big donors to go along with authoritarian and anti-democratic measures of many kinds, not just presidential power grabs but legislative and judicial steps to curtail voting and organizational rights of opponents, in essence rigging future electoral contests in a very minority rule direction.

Skocpol warned of “mechanistic over-optimism,” writing that “things will look very different if Trump is re-elected, as he may very well be.” The current state of politics “is no ordinary cyclical turn,” she notes. “I would rank this period as one of the most conflictual since the late 1960s and early 1930s and the one with the greatest potential for actual regime change since the Civil War.”

There are some political scientists who generally agree with the Skowronek theory of cyclical regime change but who raise concerns about how well Trump fits into that analytic structure.

Julia Azari, a political scientist at Marquette University, poses a basic question about attempts to place Trump within a repetitive historical context:

We have both a president who is distinct in history and an era in political time that differs from previous ones in important structural ways. This combination points to the limits of history as a clear set of instructions for what might happen next.

In an email, Azari wrote that

the overall dynamics of party competition have changed in part because, for the first time in US history as far as I can tell, race and immigration are sorted between the two parties.

In the case of Trump, Azari points out that

Presidents who violate norms, especially those about the boundaries of their power, tend to be reconstructive presidents who reset the terms of debate and the expectations for the presidency — FDR and Jackson are perhaps the clearest examples of this.

Trump, in this context, is more like a reconstructive president than a disjunctive president:

Trump has also changed the language and, I think to some degree altered the identity and agenda of the Republican Party — and of the Democrats, who are responding to him. Trump has altered how we use political language — we all use adapted Trumpisms all the time, like make X great again or a riff on “build the wall." He looms large in politics and in culture. This is not a typical disjunctive trajectory.

Azari was a student of Skowronek’s at Yale and believes his cyclical theory of regime change remains “incredibly useful for looking at politics.”

Both Azari and Skowronek acknowledge, however, that something that does not fit the theory of regime change may be taking place in American politics.