Worries about political extremism or threats to democracy have emerged as a top concern for U.S. voters and an issue where President Joe Biden has a slight advantage over Donald Trump ahead of the November election, a new Reuters/Ipsos poll showed.

Some 21% of respondents in the three-day poll, which closed on Sunday, said "political extremism or threats to democracy" was the biggest problem facing the United States, a share that was marginally higher than those who picked the economy (19%) and immigration (18%).

Biden's Democrats considered extremism by far the No. 1 issue while Trump's Republicans overwhelmingly chose immigration.