Vice President Kamala Harris has faced another setback in the polls, with a recent survey indicating she is trailing former President Donald Trump in Pennsylvania, critical to her chances of winning the presidency.

The latest blow came from a co/efficient poll conducted between September 4 and 6, which found Trump holding a slight lead among 889 likely voters in Pennsylvania. Trump received 48 percent support, while Harris garnered 46 percent, with a 3 percent margin of error.

This poll was released just hours before the highly anticipated first presidential debate between the two candidates, set to take place in Philadelphia, the largest city in the state, since Harris secured her party’s nomination in July. It will also mark the first time Trump and Harris will share the same stage.

The most populous presidential swing state has sided with the winner of the past two elections, each time by just tens of thousands of votes. Polling this year suggests Pennsylvania will be closed once more in November.

The co/efficient poll is the latest setback for Harris in Pennsylvania, where three polls from late August also showed her trailing Donald Trump. Earlier polls by Cygnal and Emerson College, conducted from August 13 to 15, also had Trump ahead by 1 point in the key battleground state.

However, not all polls show Trump ahead. A Morning Consult poll conducted between August 30 and September 8 placed Harris 3 points ahead of Trump, with 49 percent support to his 46 percent.

The race remains extremely tight, and it’s too early to draw any firm conclusions. According to FiveThirtyEight’s poll aggregator, Harris trails Trump by just 0.7 percent, while RealClearPolling shows the two candidates in a tie, each with 47.6 percent support.

For Democrats, winning big in Philadelphia and its suburbs will be key for Harris, especially in a city where Black residents are the largest racial group. At the same time, she will need to narrow Trump’s margins among white voters in rural and small-town Pennsylvania.

Losing Pennsylvania would make Harris’s path to the presidency much more difficult, given the state’s 19 valuable Electoral College votes.

Both candidates know what’s at stake and have visited Pennsylvania frequently. In August, Harris introduced her running mate, Tim Walz, in Philadelphia, with an energizing speech from Governor Josh Shapiro.

Trump, meanwhile, survived an assassination attempt in Butler County on July 14 and has since returned to Pennsylvania four times, holding rallies in Harrisburg, Johnstown, and Philadelphia. His speeches have largely focused on energy and criticisms of Harris’s energy policies.

The stakes are especially high for Harris—no Democrat has won the White House without Pennsylvania since 1948.

Before Harris became the Democratic nominee, most polls showed Trump leading President Joe Biden in the state by 2 to 7 points, according to FiveThirtyEight.