With less than two weeks to go until Election Day in the United States, polling averages show that the two leading presidential candidates, Kamala Harris and Donald Trump, are effectively tied in the most crucial swing states.

To win, a candidate must secure 270 of the 538 electoral votes up for grabs. The Electoral College votes are distributed among the states based on their relative populations.

Who is leading the way?

According to FiveThirtyEight’s daily election tracker, Vice President Harris has been leading in national polls as of Wednesday, with a 1.9 percentage point lead over former President Trump.

In a Washington Post poll released Monday, 47 percent of registered voters said they would definitely or probably vote for Harris, the Democratic Party nominee. The same percentage expressed support for Trump, the Republican Party candidate.

In contrast, a poll published Tuesday by Reuters/Ipsos showed Harris with a slight lead over Trump at 46 percent, compared to Trump’s 43 percent.

President Joe Biden defeated Trump 306 to 232 votes in the Electoral College and had a 4 percent margin in the popular vote. If the national vote margin is smaller in 2024, that’s good news for Trump — even if he trails Harris. Candidates have won the presidency despite losing the popular vote before — most recently Trump in 2016 — but never with a gap as wide as the one in 2020.

Ultimately, however, it is the Electoral College that determines the election winner, and not the national popular vote. Most states lean heavily, or very clearly, toward Republicans or Democrats.

Seven swing states, also known as battleground states, will likely determine the outcome of the 2024 elections. These are states where the battle is particularly close.

What do the polls say about the swing states?

The seven swing states are Pennsylvania (19 electoral votes), North Carolina (16), Georgia (16), Michigan (15), Arizona (11), Wisconsin (10) and Nevada (6). Together they account for 93 Electoral College votes.

But FiveThirtyEight’s average of recent surveys puts Harris and Trump within the margin of error of polls in each of these seven states. While Trump has a lead of about a percentage point or slightly more in Georgia, Arizona and North Carolina, the remaining four states – Pennsylvania, Michigan, Wisconsin and Nevada – are even closer, with less than half a percentage point separating the former president and Harris. While Trump is marginally ahead in Pennsylvania, Harris passes him in Michigan, Wisconsin and Nevada.

If the razor-thin margins of polling averages hold on election night, Trump is favored to win. But even the slightest swerve from him in these key states — or an underestimation of Harris’ support in the polls — could lead to a victory for the vice president.

In the 2020 presidential election, Georgia – where Trump is currently leading – switched from Republican red to Democratic blue after nearly three decades of voting Republican, and in Arizona – where Trump is also leading – Democrats won by a narrow margin of 0.3 percentage points.

How reliable are polls?

Election polls predict how the population might vote by surveying a sample of voters. Surveys are usually conducted by telephone or online. In some cases this is done by post or in person.

Survey trackers, which aggregate a number of polls, are weighted based on a number of factors, such as the sample size of the poll, the quality of the poll, how recently the poll was conducted, and the specific methodologies used.

Confidence in polls was undermined by inaccuracies in 2016 and 2020, according to a Pew Research Center study. In both general elections, many polls failed to accurately reflect support for Republican candidates, including Trump.

In the 2022 midterm elections, pollsters were wrong again. Only this time they underestimated support for the Democrats and predicted a Republican victory, but they were proven wrong.