Democratic presidential nominee Hillary Clinton has a six percentage-point lead over Republican rival Donald Trump, according to the latest Reuters/Ipsos tracking poll.
Ms Clinton's support has ranged from 41 percent to 44 percent since late July, and was about 41 percent in the August 11-15 online poll released on Tuesday.
Mr Trump's support has experienced wider shifts, ranging from 33 to 39 percent, while his campaign has endured controversies and distractions in recent weeks. He is favoured by about 35 percent of likely voters, according to the most recent poll.
Mr Trump has caused divisions in the Republican Party with his strong anti-immigrant and anti-Muslim rhetoric, and faced criticism from both parties earlier this month for a days-long feud with the parents of a Muslim American Army captain killed in Iraq.
Last week, 70 Republicans, including former members of Congress and Republican National Committee staff, wrote a letter calling for the party to stop helping Trump, whose actions they said were "divisive and dangerous."
The number of likely voters who picked neither Ms Clinton nor Mr Trump in the poll was nearly 24 percent.
At this point in 2012, President Barack Obama was ahead of Republican nominee Mitt Romney by nearly the same margin, favoured by 46 percent of likely voters to Romney's 41 percent, with about 13 percent picking neither candidate.
Mr Obama and Mr Romney swapped the lead in the poll several times through the summer and early autumn before the president took and held the lead in late October.
In a separate Reuters/Ipsos poll that gave respondents the option to choose from Ms Clinton, Mr Trump, Libertarian candidate Gary Johnson and Green Party candidate Jill Stein, Ms Clinton also led Mr Trump by 6 percentage points.
Of the alternative party candidates, Mr Johnson came in third with 8 percentage points. Ms Stein had about 2 percentage points.
Despite the polls, Mr Trump has claimed it would take electoral fraud for Ms Clinton to win the election.
The August 11-15 polls surveyed a sample of 1,132 and 1,131 likely voters, respectively, and had a credibility interval of 3 percentage points.
Reuters / Newshub.