And the former president jumped into the race, which pollsters say appears to have swung back in favour of Mr Newsom, and asked them to support him.
“California! You’ve got a big choice to make by September 14, and everything is on the line,” Mr Obama tweeted.
“Your vote could be the difference between protecting our kids or putting them at risk; helping Californians recover or taking us backwards. Vote “no” on the Republican recall.”
California is one of 20 states with a mechanism to recall a sitting governor and the last time the move was successful was in 2003, when Democratic governor Gray Davis was replaced by Hollywood star Arnold Schwarzenegger, who ran as a Republican.
Around 58 per cent of registered voters in California say they would back Mr Newsom against the recall vote, according to a new poll.
A Suffolk University poll, which surveyed 500 registered voters, found 41 per cent of respondents said they are in favour of a recall, while 57.8 per cent of those polled say they want Mr Newsom to remain governor of California.
The leading Republican in the race to take his job, conservative radio host Larry Elder, has pledged to reverse California’s mask and vaccination mandates if he wins.
The polling split heavily along party lines with 90 per cent of Democrats saying they will vote against the recall, and 80 per cent of Republicans saying they will vote to recall him.
Joe Biden will travel to California “early next week” to campaign for Mr Newsom, said White House Press Secretary Jen Psaki.