PHILADELPHIA — Former President Donald Trump’s polling average has pulled ahead of Vice President Kamala Harris in FiveThirtyEight’s polling tracker for the first time in Pennsylvania by an incredibly narrow margin.

The race has remained tight in Pennsylvania throughout the election cycle. But Harris had consistently — albeit marginally — led Trump in the state since President Joe Biden dropped out of the race and she was presumed to be the Democratic nominee in July, according to the tracker.

FiveThirtyEight’s new polling average shows Trump leading Harris by less than half of one percentage point in Pennsylvania, so the race, which was already viewed as a statistical tie, could now be even more of a toss-up.

Pennsylvania is a critical battleground state that both candidates see as crucial to their path to victory. The state has more electoral votes than any other swing state, and each of the last two presidential elections were decided by roughly one percentage point in the state, going for Trump in 2016 and swinging to Biden in 2020.

A Philadelphia Inquirer/New York Times/Siena College poll released earlier this month showed Harris with a nearly 4-point advantage over Trump in the state, within the margin of error, which reflected a broader trend of a tight Harris lead documented by FiveThirtyEight.

On Sunday, however, FiveThirtyEight showed Trump with 47.9% to Harris’s 47.5%, surpassing Harris’ average for the first time since she became the nominee — but by just 0.4 percentage points. That margin shrunk to 0.3 percentage points on Monday with Harris moving up to 47.6%. Both of these tiny leads are within the margins of errors and represent a continued statistical tie. Polling modeling must contend with confounding variables such as polling bias, quality, reliability, and recency.

The recent polling has shown a dip in public sentiment toward Harris and an increase of support for Trump’s campaign in the state. Over the past two months, Harris held a small polling lead over Trump, which peaked at 1.5 percentage points in mid-September

FiveThirtyEight’s polling averages for Trump and Harris are informed by at least 152 different polls, with the most recent polls weighted more heavily. Trump won four of the five latest polls that were included in the most recent Pennsylvania average, though two of those were by pollsters and sponsors that FiveThirtyEight has labeled as partisan towards the Republican Party. That being said, FiveThirtyEight weighs partisanship when creating polling averages.

Both candidates and their surrogates have been crisscrossing the state with the election just two weeks away and mail voting already underway in Pennsylvania. The candidates have paid particular attention to the Philadelphia region, which is a crucial voting block in the state.

Harris visited Malvern in Chester County on Monday after Trump tried being a fry cook at a McDonald’s on Sunday in Bucks County as both candidates zero in on the crucial Philadelphia suburbs.