Donald Trump, the Republican challenger in the US presidential contest, opened up a marginal two-percentage point lead over US President Joe Biden this week in the race to win the November election, as voters weigh the recent criminal convictions of Trump and of Biden's son, according to a new Reuters/Ipsos poll.

Some 41% of registered voters in the two-day poll, which closed on Tuesday, said they would vote for Trump if the election were held today, while 39% picked Biden, a Democrat.

Some 20% of voters in the poll said they had not picked a candidate, were leaning toward third-party options or might not vote at all in the November 5 election.

Trump's lead was within the survey's roughly three-percentage point margin of error for registered voters, many of whom remain on the fence with about five months left before the November 5 election.

A prior Reuters/Ipsos poll conducted May 31-June 1 showed Biden with a two-percentage point lead over Trump, 41% to 39%.

The latest poll found 10% of respondents would pick Robert Kennedy Jr, an anti-vaccine activist running as an independent, if he were on the ballot with Trump and Biden.

Kennedy's share was unchanged from the prior poll.

While nationwide surveys give important signals on American support for political candidates, just a handful of competitive states typically tilt the balance in the US electoral college, which ultimately decides who wins a presidential election.

Both candidates carry significant liabilities in the first US presidential election rematch in nearly 70 years.

Biden's liabilities include concerns about his age – 81 – as well as strong criticism from a slice of his Democratic Party over his support for Israel's war on Hamas.

Protests have roiled US universities in recent months, fueling concerns among Democrats that some young voters could turn against Biden.

Biden this week became the first sitting US president whose child was convicted of a crime, though the Reuters/Ipsos poll showed few voters were changing their minds over the conviction.

Trump last month became the first US president ever to be convicted of a crime, whether in office or after leaving the White House.

He is scheduled to be sentenced in July and faces potential prison time after a jury found him guilty of 34 charges stemming from a payment to an adult entertainment actress before the 2016 presidential election in exchange for her silence about an alleged encounter she says she had with Trump.

The latest Reuters/Ipsos poll, which surveyed adults nationwide, found 80% of registered voters said the conviction of Biden's son, Hunter Biden, was unlikely to sway their vote, compared to 61% who said Trump's conviction was not affecting how they would vote.

Trump, 77, also faces three other criminal prosecutions which involve charges he tried to overturn his 2020 election defeat and that he mishandled sensitive documents after leaving the presidency in 2021, though legal wrangling could keep those cases from going to trial before the November election.

Trump has pleaded not guilty to all charges.

The Reuters/Ipsos poll included responses from 930 registered voters who were surveyed online.