Let's return for a moment to what will likely be seen for years as a definitive moment in the 2016 campaign: Donald Trump's refusal during the final debate to say that he would concede the election if he were to lose. No one knows what will happen on Tuesday. But after the initial concession remarks, the internet exploded a bit with comparisons to the first peaceful transfer of power in 1800. This installment in the legitimate opposition series takes a look at the contemporary context and interrogates the 1800 example.

Trump's statement in the debate (and after) is new for a presidential campaign, but it would be silly to pretend it came out of nowhere. As the parties have become more polarized, these sorts of denials have become more common, and it's especially been a feature of the Obama years.

Media reports in the past few years present no shortage of moments like then-Senate Minority Leader Mitch McConnell noting that the top agenda item was to make Obama a one-term president (which may have been taken out of context, but were certainly understood in a particular way), and the refusal of some House Republicans to cooperate on what used to be routine votes like raising the debt ceiling. And, of course, on the fringes, there's the birther movement.

Denial of legitimate opposition isn't confined to the Republicans, of course. There was plenty of "he's not my president" during the Bush years, and Obama himself challenged input from the Republicans in 2009 by noting, "I won," at a summit on the economy. But political science research shows that Democrats and Republicans do view this question differently, with Republicans placing greater value on ideological purity while Democrats tend toward compromise.

It is this trade-off — between one's deeply held convictions on the one hand and on the other hand the deeply held conviction that democracy consists of competing perspectives, and that the right of others to act on their beliefs is equal to one's own — that informs what we're looking at now. Most of the discussion has been about Trump's flagrant disregard for norms. But we can't talk about these norms without also talking about ideological polarization.

This trade-off, and its stakes, has come up in other ways recently. When John McCain said earlier that Republicans would block Hillary Clinton's Supreme Court nominees in the event that she wins the presidency, it may have been a mere rhetorical signal. (And McCain seems to have backed off of this idea.) But it was also a claim that GOP policy convictions would overshadow the need to respect a victory by the other side.

For Democrats, the issue came up following the firebombing of a North Carolina GOP office a few weeks ago. Noting that "this is not how Americans resolve their differences," Democrats took up donations to rebuild the office. The criticism this action received fell along the same principled lines: It's all well and good to promote peaceful resolution for policy disagreements, went this line of argumentation from disgruntled progressives, but let's not forget that this particular group has stood for "bathroom bills" and voter suppression.

The idea that political opponents were so dangerous and wrong in their views that they could not be accommodated is not unique or new in American politics. In the middle of the 20th century, many of the most explosive conflicts, such as those over segregation and civil rights, occurred within rather than between parties. Trump's potential rejection of the election results has been presented as unprecedented — but in the 1950s, Southern segregationists launched a "massive resistance" effort in the face of the Brown v. Board of Education decision. It's not the same thing as rejecting an election result, but it was a pretty big challenge to the legitimacy of a national institution.

One of the historical reference points that's been cited with regard to democratic norms is the peaceful transfer of power from Federalist John Adams to Democratic Republican Thomas Jefferson. What's interesting is that historians (and historically minded political scientists) generally find that this transition predates any real sense of legitimate opposition in American politics.

In 1800, the two sides found each other just as dangerous — if not more so — than the Democrats and Republicans do now. Thomas Jefferson's 1801 inaugural address, in which he famously stated, "We are all Republicans, we are all Federalists," can be read as a rejection of legitimate opposition. Jefferson's core argument, bolstered by his actions in office, was that his side's interpretation of the Constitution was the correct one. Alternate understandings threatened the very concept of the fledgling American state.

Scholars identify the idea of legitimate opposition as having taken hold sometime in the 19th century, when Andrew Jackson and Martin Van Buren created the first mass-based political party. This is probably even pretty early, as accounts of the Whigs suggest they weren't all convinced that party competition was a good thing.

So how did peaceful alternation of power happen when the norm of legitimate opposition had not yet taken hold? The reasons are instructive for 2016, if not directly applicable. One was a belief in the process. Although the election of 1800 had a far more tumultuous counting process than any modern presidential election, the ultimate victor was the process rather than the views of either candidate.

The second is the commitment of John Adams to the American experiment. It might seem rather weak to wade through all this theory and history and come on the other side with boilerplate founder worship. And that's not precisely the point. Half of the equation is that early presidents were selected for their national reputations for statesmanship (though the success of this was hardly guaranteed — Aaron Burr came much closer to the presidency than anyone expected). The other half was the very real fear that the experiment would fail.

In contrast, American democracy in 2016 is poised to be the victim of its own success. There are norms — like legitimate opposition and respecting the process — that most people consider very important. But the decline of institutions means that the sanctions for violating those norms, even verbally, are unclear and often nonexistent.

As I noted in my last post, the United States has, as the moment, a dangerous combination of weak parties and strong partisanship. The last time this particular combination existed in US politics was just about the time that Jefferson became president in 1801. Party organizations hadn't developed yet, but sides were clear and vehemently opposed. And there was still a peaceful transfer of power.

What all the tweets and takes about this peaceful transition neglect to mention is that insofar as a presidential transition happened between these two opposing sides in the early republic, it only happened once in that context. After Jefferson left office — establishing the two-term norm — in 1809, the Federalists began to disintegrate, and an era of a diffuse, diverse set of Democratic Republicans ensued.

Jefferson, Madison, and Monroe all left after two terms — not because they lost reelection. By the time Monroe left office, there was only one party, and it wasn't much of a party in the modern sense. The ultimate result of this period was a four-candidate election in 1824 — which did install a president with questionable legitimacy, and created the conditions for a real party system to form. What followed was the real beginning of competitive mass democracy in American politics, after norms about accepting election losses and about informal presidential term limits had set in.

For all their flaws, 19th-century party machines provided the mechanisms to punish people who violated democratic norms — withdrawal of party support generally meant political exile. But even these robust institutions proved insufficient to manage the crisis that turned into the Civil War. That was, for many Southerners, a cause worthy of abandoning compromise and taking up arms.

The question of whether a major party candidate must accept election results is, well, not really a question. But the larger principle at stake is much thornier, and the dilemmas about how much ground to cede to one's opponents for the sake of compromise are real. An additional challenge lies in who can enforce those boundaries, and how they might go about sanctioning those who violate them. Having robust political institutions that can do this — that ensure that actors have a stake in the system as a whole — are especially useful when opposing parties are mired in disagreement and distrust.

That hasn't been the story of 2016. Instead, we have weakened parties alongside strong partisanship. When no one is seriously afraid that the country will disintegrate, institutional degradation causes less alarm than perhaps it should.

Weaker parties and stronger partisanship, however, is a combination rarely seen in American political history. Its closest comparison is in the very early republic. The peaceful transition of 1801, where one side stood down and accepted the victory of its political opponents, is a very important moment in the history of democratic politics. And it is all the more impressive when we consider the institutional context. But the crucial thing to remember is still that under these conditions, it only happened once.