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The Democratic Party is approaching this crucial U.S. midterm election with high expectations.
A Republican president with record-low approval ratings, an American public unhappy with rising food and bill bills, and months of polls favoring Democrats all point to a good night for Democrats on Tuesday.
Polls show Democratic candidates leading in districts well beyond the 218 seats needed to seize control of the House of Representatives, the lower house of Congress. In key Senate races, they are tied or slightly ahead of their opponents.
A recent New York Times poll showed a tie in the Senate race in South Carolina, with Donald Trump leading the state by 18 points in 2024. A recent CNN survey showed that the Democratic Party is leading in Texas, Kansas and Maine.
But are these polls accurate?
Recent American political history is littered with examples of inaccurate polls, even those conducted days before an election. Trump's performance exceeded predictions in both 2016 and 2024 when he entered the White House. He lost narrowly in 2020, when most surveys showed Democrat Joe Biden would win more easily.
Earlier this year, polls showed that Democrat Abdul El-Sayed was on track to win Michigan's Democratic Senate primary by double digits. The difference was only 1%. In Wisconsin's Democratic gubernatorial primary, a candidate who led in polls by nearly 20 points lost by less than a percentage point.
Clifford Young, president of Ipsos Public Affairs, which conducts political and market research surveys, said polling has become difficult in recent years because Americans have abandoned landlines and filtered calls, making it harder to contact them. What's more, many people contacted by pollsters are less willing to participate.
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"Conservatives, especially far-right conservatives, are inherently more anti-establishment," Young said. "They don't participate in anything. They hate the system. That's the challenge."
If Republican voters are systematically undercounted and polling companies fail to take this into account when building their voting models, their data could be skewed toward Democrats.
This is one reason why it is increasingly difficult for pollsters to predict the makeup of the electorate.
One explanation for Trump's better-than-expected performance in previous presidential elections is that his supporters - many of whom are not regular voters - flocked to the polls in higher-than-expected numbers.
This unpredictability is one of the main reasons for several apparent polling inaccuracies in recent years, although most reputable polls have an error of only a few percentage points.
In a close election, these few percentage points can make the difference between a candidate's victory and defeat. And this year, many key Senate races are within such narrow margins.
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General election polls in midterm elections have proven more accurate in recent years, in part because Trump — and his unique ability to draw disaffected Americans to the polls — is not on the ballot.
In 2022, polls show that despite Biden's sluggish approval rating, the Democratic Party will still defy conventional expectations and avoid an electoral defeat.
While Democrats ultimately lost control of the House of Representatives, the margin was narrow, and Democrats retained control of the U.S. Senate.
While this year's primary results do provide bigger surprises, Young said primaries are historically more variable and voters are more likely to leave their decisions to the last minute. This should not be taken as a sign that the current batch of general elections has been polled incorrectly.
It's common for the president's party to suffer heavy losses in midterm elections.
One of the most high-profile examples in recent years occurred in 2010, when Republicans captured more than 60 House seats from Democrats and also made gains in the Senate.
That election came against the backdrop of an economy still struggling to recover from the financial crisis and conservative concerns about President Barack Obama's health care overhaul. Polls had predicted a Democratic defeat, but not of such magnitude.
This time the roles were reversed, with the Democratic Party becoming the opposition party and economic issues becoming the focus of voters' attention. But given Trump's low approval ratings, Democrats may not do as well as history suggests or as well as some expect, for a number of reasons.
First, most of the areas involved in this election were easily won by Trump in the presidential election two years ago. For Republicans, this is like a home game.
Second, adjustments to House district boundaries over the years have resulted in fewer seats changing hands between the two parties.
Third, there are fewer swing voters as the country becomes more polarized. Some experts describe the electorate as ossified.
Additionally, Republicans have enjoyed a funding advantage that has given them hundreds of millions of dollars to spend on attack ads in the final weeks.
Poll models are designed to capture changes in fundamentals. A well-designed poll anticipates factors that may reduce its reliability.
Every single poll has an inherent margin of error, which is based on statistical uncertainty based on sample size relative to the population. Taken together, polling averages, rather than individual survey results, provide more accurate predictions.
At present, even poll trends similar to those of recent presidential elections indicate that the Democratic Party may achieve good results on the night of November 3. Moreover, polling errors could favor either party. In last year's state and special elections, Democrats performed better than most poll predictions as their voter turnout far exceeded expectations.
The sight of Trump holding rallies in the final days of the campaign in states he won easily in 2024 has boosted the hopes of Democrats who believe internal Republican polls show conservative candidates are in trouble.
However, there is always the possibility that voters may change their minds until Election Day.
Sometimes, late turns can change the dynamics of a campaign. Sometimes undecided voters—who still make up a significant portion of the electorate in many of these races—will all swing to the same side.
There is always a degree of uncertainty in polling, and managing that uncertainty is an art that goes hand in hand with science.
"I think we did a better job," Young said. "But part of the problem we've been facing is not just pollsters, but we're dealing with people. People are not easy to deal with."
This article was originally written in English. We used artificial intelligence to assist in translation and was reviewed by BBC journalists before publication. Learn more about how we use artificial intelligence.
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