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We're going to spend a lot of time over the next 87 days contemplating the possibility of a Donald Trump presidency. Trump is a significant underdog — he has a 13 percent chance of winning the election according to our polls-only model and a 23 percent chance according to polls-plus. But those probabilities aren't that small. For comparison, you have a 17 percent chance of losing a "game" of Russian roulette.

But there's another possibility staring us right in the face: A potential Hillary Clinton landslide. Our polls-only model projects Clinton to win the election by 7.7 percentage points, about the same margin by which Barack Obama beat John McCain in 2008. And it assigns a 35 percent chance to Clinton winning by double digits.

Our other model, polls-plus, is much more conservative about Clinton's prospects. If this were an ordinary election, the smart money would be on the race tightening down the stretch run, and coming more into line with economic "fundamentals" that suggest the election ought to be close. Since this is how the polls-plus model "thinks," it projects Clinton to win by around 4 points, about the margin by which Obama beat Mitt Romney in 2012 — a solid victory but a long way from a landslide.

But the theory behind "fundamentals" models is that economic conditions prevail because most other factors are fought to a draw. In a normal presidential election, both candidates raise essentially unlimited money and staff their campaigns with hundreds of experienced professionals. In a normal presidential election, both candidates are good representatives of their party's traditional values and therefore unite almost all their party's voters behind them. In a normal presidential election, both candidates have years of experience running for office and deftly pivot away from controversies to exploit their opponents' weaknesses. In a normal presidential election, both candidates target a broad enough range of demographic groups to have a viable chance of reaching 51 percent of the vote. This may not be a normal presidential election because while most of those things are true for Clinton, it's not clear that any of them apply to Trump.

A related theory is that contemporary presidential elections are bound to be relatively close because both parties have high floors on their support. Indeed, we've gone seven straight elections without a double-digit popular vote victory (the last one was Ronald Reagan's in 1984), the longest such streak since 1876-1900.

As with other theories of this kind, however, there's the risk of mistaking what's happened in the recent past for some sort of iron law of politics. Historically, the U.S. has ebbed and flowed between periods of close presidential elections — such in the late 19th century or early 21st century — and eras in which there were plenty of lopsided ones (every election in the 1920s and 1930s was a blowout).

These patterns seem to have some relationship with partisanship, with highly partisan epochs tending to produce close elections by guaranteeing each party its fair share of support. Trump's nomination, however, reflects profound disarray within the Republican Party. Furthermore, about 30 percent of Republican or Republican-leaning voters have an unfavorable view of Trump. How many of them will vote for Clinton is hard to say, but parties facing this much internal strife, such as Republicans in 1964 or Democrats in 1972 or 1980, have often suffered landslide losses.

Perhaps the strongest evidence for a potential landslide against Trump is in the state-by-state polling, which has shown him underperforming in any number of traditionally Republican states. It's not just Georgia and Arizona, where polls have shown a fairly close race all year. At various points, polls have shown Clinton drawing within a few percentage points of Trump — and occasionally even leading him — in states such as Utah, South Carolina, Texas, Alaska, Kansas and even Mississippi.

Just how bad could it get? Let's start by giving Clinton the 332 electoral votes that Obama won in 2012. That's obviously not a safe assumption: The race could shift back toward Trump, and even if it doesn't, Clinton could lose states such as Iowa or Nevada, where her polling has been middling even after her convention bounce. But as I said, we're going to focus on Clinton's upside case today.

So I'm going to list the states Romney won in order of how easy it is for Clinton to flip them, according to our polls-only model. The number in parentheses by each state represents the point at which the model estimates it would flip to Clinton, based on her lead in the national popular vote. For instance, South Carolina (+9.5) means that Clinton would be favored in South Carolina if she leads by at least 9.5 percentage points nationally, but not by less than that. These projections are based on where the model has each state projected currently, along with each state's elasticity score, a measure of how