Donald Trump´s victory in the US presidential elections four years ago raised unprecedented doubts about whether opinion polls could be trusted. Is it reliable this time?
Sixteen days before the November 3 election, Democrat Joe Biden is ahead of the Republican president by nine percentage points nationwide, according to poll rates published by RealClearPolitics.
But in the United States, candidates win the White House through the electorate, not the popular vote.
In 2016, Trump lost the popular vote to Hillary Clinton, but won enough states to amass the electorate he needs to become president.
This year, six states are seen as key to reaching the White House: Florida, North Carolina, Arizona, Wisconsin, Pennsylvania and Michigan.
But if the polls are correct, Biden appears to be in a better position in this regard, although he is sometimes within the margin of error, and his progress ranges from 1.7 percentage points in Florida to 7.2 in Michigan.
On the eve of the election, the polls correctly predicted a slight lead for Clinton nationally, but she "missed some of the swinging midwestern states" that Trump ultimately won, Chris Jackson of the Ipsos Center for Public Affairs told AFP.
One reason for this, he said, was the underrepresentation of the white population without college degrees who voted for Trump.
Most polling institutes indicate that they have made corrections to their general methodology to exclude such errors in the upcoming elections.
This time, polls are being conducted with greater interest and more frequently in critical states that did not see enough polls last time.
In addition, pollsters are pointing to the stability of the results this time. Since the spring, Biden has led by a rate that has never dropped below 4 percentage points.
Ultimately, in a country so polarized, there are far fewer undecided voters who might turn the tide at the last minute.
Some feel that there are voters who have reservations about declaring their preference for Trump, given the controversy surrounding him.
Trump said, "The polls were wrong last time, and they are more wrong this time."
The Trafalgar Group, the polling firm favored by Republicans and employing an approach that takes into account the potential for voter reticence, was among the few who predicted Trump´s 2016 victory in Pennsylvania and Michigan.
But this time it is giving Biden an advantage in crucial states like Pennsylvania and Wisconsin.
Four years ago, Trump was just a new businessman in the political arena. Consequently, it is often difficult for pollsters to evaluate this type of candidate.
Jackson comments on this by saying that "everyone who sees him now is not surprised to the same degree about Donald Trump."
According to calculations made by The New York Times, Biden would win even if the current polls in each state are as wrong as they were four years ago.
"According to our average polls, Biden is more likely to win in Texas, which will give him more than 400 electoral votes, than President Trump is likely to win in traditionally swing states like Pennsylvania and Nevada," New York Times journalist Nate Kohn wrote recently.
Still, pollsters and analysts are cautious in pointing out that voting intentions cannot suffice as expectations and that there is a margin of error.
Election campaigns can transform, as the 2016 presidential election was likely decided at the last minute.
And it is reported that 16 days before that election date, Five Thirty Eight favored Clinton´s victory by 86 percent, which is something that has been repeated with Biden now.
In the United States, voter registration shifts dramatically, which makes it especially difficult to predict turnout.
Trump indicates when addressing his supporters at his election rallies that the momentum is in his favor, but will this be translated into the ballot box?
Will Democrats who weren´t enthusiastic about Clinton, who initially thought she had already won, line up behind a fading Biden to dislodge Trump?
How will the epidemic affect?
"We will have a mail vote and early vote, which will be at historic levels," Jackson says.
"We don´t know what the impact of that will be. There are many complex factors that will overlap and these are the things that are difficult for the polls to calculate," he added.
