Harris stands at 48 per cent against Trump's 46 per cent in Pennsylvania, the UMass Lowell's Center for Public Opinion said.
Biden's lead has shrunk over the last few days, as Trump and his family have virtually carpet bombed the key battle ground states, including as many as 15 rallies by the president.
However, the 68-year-old leader continues to maintain lead in some of the key battle ground states, other polls said.
The US presidential election slated to be held in November appears to have tightened as a series of latest national polls projected that Republican Donald Trump has gained some ground in the last week against Hillary Clinton of the Democratic Party.
Analysts believe the main reason for Trump's popularity surge is that he now enjoys wider support from Republican voters after his decisive win in Indiana earlier this month.
CBS said Trump leads among white men, whites without a college degree, and seniors.
A week before the US presidential elections, Republican nominee Donald Trump has taken a slender lead of one percentage point against his Democratic rival Hillary Clinton for the first time since May in a major national tracking poll.
Due to the coronavirus pandemic, he had suspended his election rallies for the past three months.
Obama's national lead is now 2.1 point, RealClearPolitics said based on the average of all the recent national polls; the latest one being that of the Time magazine, according to which the US President now leads over Romney by five points in the most important battle ground state of Ohio.
Various poll surveys ahead of the November 6 United States Presidential elections have come out with mixed results, indicating a possibly close contest between incumbent Barack Obama and his Republican rival Mitt Romney.
However, the margins of all these polls come within the range of statistical error. As such experts are now saying this as a very close race
Indian American Louisiana Governor Bobby Jindal has a good chance of being selected as vice-presidential running mate of Mitt Romney, the presumptive Republican presidential nominee, a media report has said.
The eight-point advantage that Clinton has is virtually unchanged from her nine-point lead last week.
Biden, 77, who served as vice president of the US for eight years from January 2009 to January 2017, would deliver his acceptance speech on Thursday.
Likely voters who watched the first presidential debate are twice as likely to say the debate made them think better of Clinton than worse.
Donald Trump on Thursday reached the magic number of 1,237 delegates, making the real estate mogul the sole claimant to be the Republican party's presidential nominee for the November polls.
Another major media outlet for the first time projected Hilary's electoral college votes below the half way mark of 270.
The 77-year-old former US vice president on Friday night took his tally of pledged delegates over the halfway mark of 1,991 from a total of 3,979, thus becoming eligible to earn the Democratic Party's presidential nomination.
"We don't know anything about Hillary in terms of religion," Trump told a group of evangelical leaders, adding, "she's been in the public eye for years and years, and yet there's no -- there's nothing out there."
Prior to his speech Trump tossed masks into the crowd.
Amidst reports that Donald Trump is gaining ground in key battle states in the US, the Republican presidential nominee on Thursday said that Americans are "ready to discard failed political establishment" that disrespects upon hardworking people.
The Democratic presidential nominee has gained a whopping 15 per cent national lead owing to the recent gaffes made by her Republican rival.
Trump, 74, in his acceptance speech from the South Lawns of the White House amidst cheers from his supporters on Thursday night, said: "My fellow Americans, tonight, with a heart full of gratitude and boundless optimism, I proudly accept this nomination for President of the United States".
Bernie Sanders alleged that Clinton is not qualified to be the president.
Haley's endorsement is seen as a big boost for Rubio, but this does not guarantee him a win in South Carolina, despite the fact that the Indian-American is one of the most popular governor's in the state's history.
Locked in a neck-and-neck battle, Hillary Clinton and Donald Trump have made a last minute dash to key swing states to woo undecided voters as major polls on the final weekend before the election day showed the race for the White House was too close to call.