Ex-President Barack Obama has recorded videos in support of his former vice-president and spoken by video link at the Democratic National Convention in August, but has not yet appeared at a live rally in support of Joe Biden.

Former US President Barack Obama will hit the campaign trail for his old running-mate Joe Biden next week.

Obama will headline a presidential campaign rally in Philadelphia, the capital of Pennsylvania on Wednesday October 21.

It will be the first time Obama has appeared publicly in support of Biden's campaign to win the presidency from incumbent Donald Trump, although the ex-president and his wife Michelle have released videos in support of the Democratic Campaign and gave a speech at the virtual Democratic convention in August. 

Obama's big comeback could be quite a low-key affair, however. Biden's campaign has said it is deliberately keeping events small to avoid the risk of spreading the coronavirus. By contrast Trump's rally at Des Moines airport in Iowa on Wednesday night saw a turnout of 10,000.  

Pennsylvania, Biden's home state, from Trump is a key Democratic target for winning the presidency. The state has 20 votes in the electoral college system, making up a large slice of the 270-vote target for candidates to win the presidency.

Trump became the first Republican to win the state since George Bush in 1998 when he was elected in 2016. In this campaign the president has made much of flip-flopping by Biden and his running-mate Kamala Harris on whether or not they would ban fracking and fossil fuels, a major part of Pennsylvania's economy.