Democratic challenger Sara Gideon holds a slight lead over incumbent Republican Sen. Susan Collins in Maine’s U.S. Senate race, according to a poll released Thursday by Quinnipiac University.

The poll shows 47 percent of respondents favored Gideon, while 43 percent favored Collins and 6 percent remained undecided. The poll sampled 807 self-identified registered voters in Maine by telephone between July 30 and Aug. 3. It has a margin of error of plus or minus 3.5 percentage points.

The poll also shows a large lead for former Vice President Joe Biden in his challenge against President Trump. Biden, the presumptive Democratic nominee to challenge Trump, was favored by 52 percent of respondents, compared to 37 percent who favored the president.

Sixty percent of respondents said they disapprove of Trump’s response to the coronavirus, 60 percent said Biden would do a better job handling the issue of racial inequality, and 55 percent said Biden would do a better job responding to the pandemic. Fifty percent said Biden would do a better job with the economy.

Quinnipiac University polling analyst Tim Malloy said the closeness of the race between Gideon and Collins was reflective in many ways of voters’ views on Trump.

“(Collins) has both defied President Trump and backed him to the hilt,” Malloy said of the last Republican member of Congress from New England. “An embattled Republican in a northeastern state, Sen. Collins faces the political challenge of her life.”

The poll found that 88 percent of voters have made their choice in the Senate race while just 11 percent say they could still change their mind.

In other findings, 52 percent disapprove of the way Collins is handling her job in the Senate, while 60 percent said they approved of the work being done by Sen. Angus King of Maine, an independent who caucuses with Democrats.

The poll is the third since July 6 showing Gideon with a slight edge on the long-serving Republican, who in 2014 won reelection with nearly 70 percent of the vote.

A poll in early July from the left-leaning Public Policy Polling gave Gideon a 4-point lead, and a Colby College poll released near the end of July showed Gideon leading by 5 points.

The candidates are locked in what is expected to be toughest challenge Collins has seen. Their campaigns have collected more than $41 million combined and have already spent $30 million of that – making the race the most costly in state history. Outside groups, including several well-heeled national super political action committees, also are shoveling cash into the race.

The Quinnipiac poll also suggests that Maine voters are largely satisfied with Gov. Janet Mills and her handling of the COVID-19 pandemic, with 64 percent saying they approve of Mills’ response to the virus.