As the presidential campaign heats up, the Guardian is tracking the latest polling in eight states that could decide the election

Joe Biden is leading Donald Trump in the national polls for the presidential election.
But that doesnt guarantee the Democratic candidate victory. Hillary Clinton also had a clear lead over Trump in the polls for almost the entire 2016 campaign. She ended up losing in the electoral college.
Because the presidential voting system assigns each state a number of electoral college votes, which go to the states victor regardless of the margin of victory, a handful of swing states will probably decide the election and be targeted heavily by campaigners.
Each day, the Guardians poll tracker takes a rolling 14-day average of the polls in eight swing states.
In order to track how the race is developing in the areas that could decide the election, six of the eight states we focused on were those that flipped to Trump in 2016 after backing Barack Obama in 2012. Arizona and North Carolina were also added due to what they might tell us about a shifting electoral landscape they could emerge as vital new swing states this year.
We must caution that the polls particularly some swing state polls severely undercounted Trump supporters in 2016. We are not certain, despite assurances, that they they have corrected this. Additionally, they may be over-counting Democratic support (more people may say they will vote for Biden than actually turn out).
We present the latest polls with those caveats to be borne in mind.
The latest polling average puts Biden ahead of Trump nationally.
While the national poll tracker is a poor indicator of how the crucial swing states will sway the election, a strong polling lead across the country can point to how the race will develop.
Each day, the Guardians national poll tracker takes a 14-day average of national voting intention polls.
On Tuesday 3 November 2020, Americans will vote for their next president, with a choice between Donald Trump, the Republican incumbent, or his Democratic challenger, Joe Biden.