A voter casts his presidential ballot at a polling station on Staten Island in 2012. This year, not all political models agree on who the winner will be. (Keith Bedford/Reuters)

For those who wish this long and often dismal presidential campaign were over, help is already here. To the rescue have come the forecasters — political scientists with prediction models that have already called the election, in some cases many months ago.

Their work will soon be published collectively in the upcoming issue of the journal PS: Political Science and Politics. On Friday, a handful of the forecasters appeared in Philadelphia at the annual meeting of the American Political Science Association to offer their thoughts. Some of their analyses have been carried on Larry Sabato’s Crystal Ball website at the University of Virginia.

Lost in the extraordinary amount of attention that has been focused on the strengths and weaknesses of Hillary Clinton and Donald Trump is the reality that the outcome of presidential elections often depends as much or more on fundamentals as on candidate performance. It’s not that campaigns and candidates don’t matter, but events play out against a backdrop of attitudes and conditions that often favors one side over the other from the very start.

James E. Campbell of the University at Buffalo offered an analogy of a card game to make this point. Everyone at the table is dealt a hand, he said in a recent phone interview. Some will play those hands better than others. Someone also might get lucky with a draw (the equivalent of a helpful outside event in a campaign). In the end, however, the player who was dealt the best hand has a greater chance of winning.

Sometimes there is unanimity — or close to it — among the political science models. Not this year. Most see Clinton as the winner, but at least two models project that, on Inauguration Day, it will be Trump taking the oath of office. The modelers are standing by their projections, though with varying degrees of confidence because Trump is a wild-card candidate. Two of the political scientists, because of their own political leanings, hope their models turn out to be wrong this year.

Campbell, who wrote the new book “Polarized: Making Sense of a Divided America,” has prepared the introduction and overview for the individual forecasts that will be published this fall. That introduction provides a quick tour of the kinds of underlying forces shaping this and all presidential campaigns.

This is an open-seat election, making a close outcome more likely than when an incumbent seeks a second term. Another force that suggests the 2016 winner’s margin should be relatively narrow is the depth of polarization in the country, which seems to have lowered the ceiling and raised the floor for each candidate’s support level in recent elections. A third factor pointing toward a close election is presidential approval. President Obama’s is high enough to give Clinton some help, but not so high as to guarantee victory.

Public opinion polls taken before the two party conventions have been other useful indicators for modelers. This year, they have pointed to a Democratic victory. But pointing in the other direction are indicators, often measured through economic performance, that suggest frustration with the incumbent party. The country’s foul mood and the economy’s slow growth should help Republicans this year.

“The early signs and readings of the context in which the campaigns will be run would suggest that 2016 was shaping up with a tilt to the Republicans until they nominated the bombastic Donald Trump,” Campbell writes. “It was not a ‘sure thing’ for the Republicans before their nomination and it . . . does not appear to be a ‘sure thing’ for the Democrats after the Republicans’ astonishing nomination.” But Campbell calls that conclusion “loose conjecture” and says that the forecast models — no two alike — offer a more detailed projection of the outcome on Nov. 8.

One model, by Robert Erikson of Columbia University and Chris Wlezien of the University of Texas, points to Clinton winning with 52 percent of the two-party popular vote. (Actual vote percentages for Clinton and Trump will be lower because of the presence of Libertarian Gary Johnson and the Green Party’s Jill Stein on the ballot.) That model combines post-convention polls with the results from the index of leading economic indicators.

These 10 states are in play in the 2016 election. Here is where they're polling as of August and how much weight they'll have in November. (Sarah Parnass/The Washington Post)

Michael Lewis-Beck of the University of Iowa and Charles Tien of Hunter College also see a Clinton victory, with just 51 percent of the two-party popular vote. Tien said that translates to a narrow electoral college majority for Clinton of 274 votes.

Andreas Graefe of LMU Munich and J. Scott Armstrong of the Wharton School at the University of Pennsylvania cite four different models, all of which point to a victory by Clinton larger than some of the other forecasts.

One outlier is Helmut Norpoth of Stony Brook University. His model takes into account sentiment for a change in parties, but most important, and unusual, is his reliance on performance by the major-party candidates during the early presidential primaries, in this case New Hampshire and South Carolina. On that basis, he predicted last spring that Trump would win the election and said the prediction came with an 87 percent certainty.

When I spoke with Norpoth a few days ago, he was admittedly nervous. “I do worry. . . . I’m clearly sort of the odd man out,” he said. But, he added, “it’s not a foregone conclusion that he’s [Trump] going down the tubes.”

Alan Abramowitz of Emory University uses what he calls a Time for Change Forecasting Model. His model does not rely on polling data but instead takes into account the incumbent president’s approval rating at midyear, the growth rate of real gross domestic product in the second quarter of the election year and whether the incumbent president’s party has held the White House for one term or more than a term.

On that basis, his model predicts a narrow victory for Trump. But Abramowitz also suggests that Trump could underperform. “A model like mine that relies entirely on fundamentals is likely to miss the result because Trump is such an atypical candidate,” he said.

Abramowitz, who has been openly critical of Trump this year, said he would rather his model be wrong this time. In his paper, he writes: “The Time for Change model will most likely make its first incorrect prediction in 2016. I will not be upset.”

Campbell has the same mixed emotions about his two forecasts, each of which combines economic data with polling data. One of his forecasts, based in part on the effect of the conventions, projects Clinton as a narrow winner. His second model awaits post-Labor Day polling results but is pointing toward the same outcome.

“Frankly, I don’t like my forecasts from the standpoint of politics,” he said. “I’m a conservative Republican and I’m predicting that Clinton will win the election.”

Campbell said that, during most election years, he prepares his own campaign memorabilia to share with friends. This year it’s a bumper sticker, and it captures the frustrations of an electorate that is not happy with the two major-party candidates. “The first line says, ‘My candidate is an idiot,’ ” he said. “The second line is, ‘Your candidate is worse.’ ”

There are other predictors of the 2016 election, including those based entirely on polling data, including Nate Silver’s FiveThirtyEight.com and the New York Times’s Upshot. And then there are some benchmarks that have had a string of successes. As Erikson noted, “Since 1952, the person leading two weeks after the second convention has never lost the popular vote.”

That group, of course, includes Al Gore. He was the forecasters’ favorite in 2000, with models predicting a solid Gore victory. Gore did manage to win the popular vote but never made it to the White House. Even the best models can’t account for every possibility.