美國大選民調：哈里斯還是川普誰領先？

On November 5, voters in the United States will head to the polls to select their next president. This election was initially set to be a rematch of the 2020 election, but everything changed in July when President Joe Biden decided to end his campaign and endorse Vice-President Kamala Harris. Now, the big question is whether America will elect its first female president or if Donald Trump will secure a second term. As election day approaches, we will closely monitor the polls to understand how the race for the White House is shaping up. Since Kamala Harris entered the race at the end of July, she has maintained a slight lead over Trump in the national polling averages. In the early weeks of her campaign, she experienced a surge in her polling numbers, building a lead of nearly four percentage points by the end of August. The polling numbers remained relatively stable throughout September and early October, but they have tightened in recent weeks. The national polls provide a useful overview of a candidate's popularity across the country, but they are not the most reliable way to predict the election outcome. This is due to the United States' electoral college system, where each state is allocated a number of votes based on its population size. A total of 538 electoral college votes are available, and a candidate must secure 270 to win the presidency. While there are 50 states in the US, most of them consistently vote for the same political party. This means that only a few states, known as battleground states or swing states, will ultimately determine the election's outcome. Currently, the leads in these swing states are so narrow that it is challenging to ascertain who is genuinely ahead based on the polling averages. Polls are designed to provide a general sense of public sentiment towards a candidate or issue, rather than predict election results with pinpoint accuracy. It is also crucial to keep in mind that the individual polls used to create these averages have a margin of error of approximately three to four percentage points, meaning either candidate could be performing better or worse than the current numbers suggest. Analyzing the trends since Harris joined the race reveals some interesting differences among the states. In Arizona, Georgia, Nevada, and North Carolina, the lead has shifted back and forth several times since early August, but Trump currently holds a slight advantage in all of them. Conversely, in Michigan, Pennsylvania, and Wisconsin, Harris has maintained a lead since August, sometimes by two or three points. However, the polls have tightened significantly, and Trump now has a very narrow lead in Pennsylvania. These three states were once strongholds for the Democratic party before Trump flipped them in 2016. Biden managed to reclaim them in 2020, and if Harris can do the same, she will be well-positioned to win the election. Notably, on the day Biden withdrew from the race, he was trailing Trump by nearly five percentage points on average across the seven swing states. Pennsylvania is particularly crucial for both campaigns, as it has the highest number of electoral votes among the seven states, making it easier to reach the necessary 270 votes. The polling averages we see are created by a group called 538, which is part of the American news network ABC News. To generate these averages, 538 collects data from various individual polls conducted both nationally and in battleground states by numerous polling organizations. As part of their quality control process, 538 only includes polls from companies that meet specific criteria, such as being transparent about the number of people surveyed, when the poll was conducted, and how the polling was carried out (whether through phone calls, text messages, or online surveys). However, it is essential to approach these polls with caution. In the last two elections, polls underestimated Trump's support, and the national polling error in 2020 was the highest it had been in 40 years, according to a review by polling experts. The polling miss in 2016 was attributed to voters changing their minds in the final days of the campaign and the over-representation of college-educated voters, who were more likely to support Hillary Clinton. In 2020, experts pointed to difficulties in getting Trump supporters to participate in polls, but they acknowledged that it was impossible to pinpoint the exact cause of the polling error, especially since the election took place during a pandemic and saw record voter turnout. Pollsters have made numerous adjustments since then, and the polling industry experienced one of its most successful election cycles in US history during the 2022 midterm elections. However, it is important to note that Donald Trump was not on the ballot during those midterms, and we will not know until after election day whether these changes can effectively account for the influx of irregular voters that Trump tends to attract.