With less than four weeks left to go until election day, the race for the White House is as close as ever.

Nationally, Kamala Harris remains a couple of percentage points ahead of Donald Trump - a lead she has had since she entered the race at the end of July.

But the US election is won and lost in the handful of states where both candidates stand a chance of winning - those known as the swing states.

The biggest prize in the seven swing states in this election is Pennsylvania, because it has the highest number of electoral college votes on offer and therefore makes it easier for the winner to hit the required 270 votes to become president.

Election polls - Is Harris or Trump ahead?

So what do the polls tell us about who might win there?

Back in July, the polls were looking bleak for Democrats in Pennsylvania. Joe Biden’s numbers had taken a hit after his lacklustre performance in the first presidential debate and Trump’s lead over him had grown to more than four percentage points, as you can see in the chart below.