Joe Biden has a marginal 1 point lead over Donald Trump ahead of November presidential election - poll

U.S. President Joe Biden had a marginal 1 percentage point lead over Donald Trump ahead of the November presidential election as each candidate secured enough support from their parties to appear on the ballot, a new Reuters/Ipsos poll found.

Some 39% of registered voters in the one-week poll, which closed on Wednesday, said they would vote for Biden, a Democrat, if the election were held today, compared with 38% who picked Republican former President Trump. Biden's lead was within the survey's 1.8 percentage point margin of error.

Many voters remain undecided, with 11% saying they would vote for other candidates, 5% saying they would not vote, and 7% saying they did not know or refusing to answer.

Both candidates carry significant liabilities in the first

U.S. presidential election rematch

in nearly 70 years, with voters concerned about Biden's age -- 81 -- and Trump's upcoming four criminal trials, including on charges of trying to overturn his 2020 election defeat.

The poll, which surveyed adults nationwide, included many ways to measure support for Biden and Trump, 77, and most pointed to a close race.

Trump had a marginal lead among all respondents, but Biden's lead among registered voters was significant because people who are already registered to vote are more likely to do so in November. Only two-thirds of eligible voters turned out in the 2020 presidential election in which Biden defeated Trump.

In the seven states where the election was closest in 2020, a group that could again prove pivotal in November, Trump led Biden 40% to 37% among registered voters. While nationwide surveys give important signals on who America will vote for, just handful of competitive states typically tilt the balance in the U.S. electoral college, the ultimate decider in presidential elections.

With many voters unenthused by either Trump or Biden, the new poll showed independent candidate Robert F. Kennedy Jr backed by 15% of registered voters should he appear as a third candidate on the ballot, down from 17% in a January survey.

It appeared that Kennedy could siphon similar shares of votes from Trump and Biden. When poll respondents were asked to choose between Trump and Biden without any other options, Biden led 50% to 48% among registered voters, with 2% refusing to answer the question.

While Trump easily defeated former South Carolina Governor Nikki Haley in the Republican Party's party nominating contest, clinching enough delegates on Tuesday to be the party's candidate, he has vulnerabilities among independents and even within his own party.

Only about 37% of Haley's supporters plan to vote for Trump now that she has dropped out of the Republican contest, the poll found. Some 16% said they would vote for Biden and the rest said they would vote for someone else or not vote at all.

Following a controversial ruling by a conservative court in Alabama that the frozen embryos used in fertility treatments should be considered children, the new poll showed only a quarter of registered voters agreed with that view, while 57% disagreed and the rest were unsure.

The Reuters/Ipsos poll collected responses online nationwide from 4,094 U.S. adults, including 3,356 registered voters. It had a margin of error of 1.8% for registered voters and 1.7% for all respondents.