Will Trump voters — like these at a rally, waving goodbye to him as he leaves — defy the polls and ship him again to the White Home? Olivier Touron/AFP/Getty Pictures

The storyline of the presidential marketing campaign appears to be solidifying, as polls present Joe Biden sustaining a large lead over President Donald J. Trump.

However the lead will not be insurmountable, and the election will not be over.

The historical past of polling in trendy elections means that the endgame might but be altered by quite a lot of disruptive situations.

Not one of the following narrative-altering situations will be thought-about a certainty. However just one is slightly far-fetched. All are knowledgeable by the content material of my newest e book, “Misplaced in a Gallup: Polling Failure in U.S. Presidential Elections.”

Listed below are descriptions of 5 potential situations, so as of chance. In a bow to even-handedness, a actuality test is appended to every of them.

Did FBI Director James Comey’s assertion that the company was reopening its investigation into Hillary Clinton’s emails – made 11 days earlier than the 2016 election – badly harm her possibilities of profitable?

Cliff Owen/AP

1. A robust late October shock disrupts the marketing campaign trajectory

Jarring, out-of-the-blue developments have occurred typically sufficient in presidential election campaigns as to be nearly anticipated. Bear in mind James Comey’s announcement 11 days earlier than the 2016 election that the FBI had reopened its investigation into Hillary Clinton’s emails? It could have shifted sufficient votes in battleground states to elect Trump.

To change the trajectory in 2020, the October shock in all probability must be akin to a really public meltdown by Joe Biden – a “mendacity, dog-faced pony soldier” second on steroids – that will clearly sign he’s less than the job. Whereas Biden’s gaffes, exaggerations and garbled feedback have been on frequent show in the course of the 2020 marketing campaign, they haven’t been concentrated or dramatic sufficient to puncture his benefit in preelection polls.

Why it gained’t occur: Presidential elections could also be rising proof against late October surprises, given the recognition of early voting and the arrival of intensive mail-in balloting. As such, thousands and thousands of People can have solid ballots for president nicely earlier than Election Day – tempering the influence of any late October shock.

2. Important polling errors happen in key states, sufficient for Trump to win an electoral vote majority

In states resembling Wisconsin and Michigan, which have been essential to the result in 2016, preelection polls pointed to a transparent lead for Hillary Clinton – a bonus that evaporated when votes have been counted. Clinton’s polling benefit in Wisconsin, for instance, was 6.5 proportion factors at marketing campaign’s finish; Trump carried the state by lower than some extent. Such errors are usually not fully out of the query in 2020.

Why it gained’t occur: This situation basically is a 2016 replay. If the historical past of election polling tells us something, it’s not to count on elections, or polling failures, to duplicate themselves. Not solely that, however significantly extra scrutiny is being dedicated to polling in battleground states in 2020 than 4 years in the past. Such consideration could render this situation unlikely.

Hillary and Invoice Clinton celebrating his 1996 re-election victory over GOP candidate Bob Dole, which wasn’t the blowout many pollsters had predicted.

David Hume Kennerly/Getty Pictures

3. The 1996 situation materializes

This can be a nuanced situation that recollects Invoice Clinton’s 1996 reelection, when he defeated Republican Bob Dole by 8.5 proportion factors – a snug margin however not the blowout many polls and pollsters had anticipated. On the finish of October 1996, veteran California pollster Mervin Area declared Clinton was “heading for as large a win” as Ronald Reagan’s 18-point landslide in 1984, when he carried 49 states.

The polls in 1996 didn’t miss on the winner, however some have been nicely off the ultimate margin. For instance, the end-of-campaign CBS Information survey estimated Clinton’s lead at 18 factors, practically a 10-point miss.

Why it gained’t occur: Polling failure in presidential elections isn’t duplicated. A rerun of the 1996 situation depends upon Biden holding a double-digit polling lead within the marketing campaign’s remaining phases – a time when presidential races are likely to tighten. Biden’s combination lead in nationwide polls, as compiled by the RealClearPolitics web site, stood at 8.6 proportion factors two weeks earlier than Election Day.

On Feb. 9, 2020 in New Hampshire, Joe Biden referred to as the girl with the microphone ‘a mendacity, dog-faced pony soldier’ after she requested him about his poor Iowa caucus efficiency.

AP Picture/Elise Amendola

4. ‘Shy Trump’ voters emerge en masse, decisively so in battleground states

This concept maintains that as a result of they wish to keep away from disapproval, some Trump supporters conceal their preferences from pollsters and others. They’re reluctant to acknowledge assist for such a divisive character.

As a result of they’re guarded about their intentions, these undercover supporters skew polling knowledge as a result of they supposedly are so onerous to search out, or fail to reply candidly when they’re interviewed. By turning out in nice numbers, the speculation goes, “Shy Trump” voters might tip the electoral vote to the president.

Why it gained’t occur: Such voters in all probability don’t exist in numbers massive sufficient to change a nationwide election. Assessments by pollsters and polling organizations have instructed as a lot. In addition to, Trump’s out of doors rallies point out that his supporters aren’t precisely reserved about expressing political preferences.

5. An epic polling collapse, akin to that of 1948, takes place

The well-known “Dewey defeats Truman” election signaled a surprising and never-since-duplicated breakdown of nationwide election polling. George Gallup and different pollsters confidently predicted President Harry Truman’s loss to Republican Thomas E. Dewey – and their polling set expectations for the nation’s press and pundits. Truman gained by 4.5 proportion factors within the best polling embarrassment in U.S. presidential historical past.

Why it gained’t occur: Polling since 1948 has develop into extra subtle in methods and extra quite a few in practitioners. It’s nearly inconceivable that up to date election pollsters might be profoundly and uniformly unsuitable in 2020. Whereas 1948 does provide an intriguing potential precedent, this can be a most inconceivable situation.

[Get our most insightful politics and election stories. Sign up for The Conversation’s Politics Weekly.]

W. Joseph Campbell doesn’t work for, seek the advice of, personal shares in or obtain funding from any firm or group that will profit from this text, and has disclosed no related affiliations past their educational appointment.