Around 50% said they would vote for Obama, while only 39% said they would vote for Trump. Others said they either didn't know or wouldn't vote.

The poll also showed Biden, whose candidacy is in doubt after a disastrous debate against Trump last week, in a 40% to 40% dead heat with the Republican.

Other potential Democratic candidates all polled lower than Trump, with Vice President Kamala Harris trailing Trump at 43%-42%, California Gov. Gavin Newsom trailing 42%-39% and Michigan Gov. Gretchen Whitmer at 41%-36%.

The chances of Obama taking on Trump, though, are remote, with the former first lady having repeatedly ruled out standing for office.

As recently as March, in a statement to NBC News, she said she would not be running.

"As former First Lady Michelle Obama has expressed several times over the years, she will not be running for president," her communications director said. "Mrs. Obama supports President Joe Biden and Vice President Kamala Harris' re-election campaign."

The statement was in response to a flurry of speculation that she could replace Biden as the Democratic candidate this year.

Obama, who campaigns for causes including healthy eating and gender equality, has long been among the most popular political figures in the US.

In 2020, Biden said he'd choose her as his running mate "in a heartbeat" if she decided to stand.

Obama campaigned for Biden in 2020, delivering the keynote speech at the DNC convention where she warned of the dangers of a second Trump term. She's kept a lower profile during this year's election but had been expected to campaign for Biden during the final stretch of the election.

Her husband, former President Barack Obama, has stood by Biden despite the shaky debate performance but has privately remarked that Biden's road to reelection has become difficult following the debate, The Washington Post reported.