Hillary Clinton holds a five percentage point lead over Republican rival Donald Trump, according to a the latest poll, down only slightly since the FBI said it was reviewing new emails in its investigation of the former secretary of state.
Some 44 per cent of likely voters said they would support Clinton, while 39 per cent said they would support Trump, according to the October 26-30 Reuters/Ipsos poll.
Clinton had held a 6 point advantage over Trump in the five-day tracking poll last Thursday.
Other polls have shown Clinton's lead slipping more sharply. Real Clear Politics, which averages the results of most major polls, shows that Clinton's lead declined from 4.6 points on Friday to 2.5 points on Monday.
Federal Bureau of Investigation Director James Comey told Congress in a letter made public on Friday that his agency was looking into new emails that may be connected to Clinton, who had been probed by the FBI over her use of a private server and how she handled classified information while America's top diplomat.
The FBI has revealed very little to the public about the new emails under investigation, except that they were uncovered during an unrelated investigation into the estranged husband of a top Clinton aide.
In a separate poll that included alternative-party candidates, 43 per cent supported Clinton, while 37 per cent supported Trump, 6 per cent supported Libertarian candidate Gary Johnson and 1 per cent supported Jill Stein of the Green Party.
The polling determines likely voters according to a number of factors including voting history, registration status and stated intention to vote. It assumes that 60 per cent of eligible Americans will vote. The result of the 2016 election will vary greatly depending on how many voters actually cast a ballot.
Currently, Clinton leads Trump in both high and low turnout scenarios, according to the latest poll. Her advantage holds at 5 points if 55 per cent of eligible voters participate, and it rises to 6 points if 70 per cent of Americans cast a ballot.
