The Philly area has played a key role in delivering Pennsylvania. Here are trends to watch for on Election Day.

Believe it or not, Election Day is officially one day away.

In the run-up to Nov. 5, Pennsylvania has become the de facto center of the American political universe, poised to play a determining role in the 2024 election. But Philadelphia — the key battleground state’s largest city — and its populous suburbs have a big part in deciding whether Vice President Kamala Harris or former President Donald Trump wins the state’s 19 Electoral College votes.

Both campaigns have been vying for the state’s crucial votes, exemplified by 33 trips to Philadelphia and its collar counties (21 for Harris-Walz and 12 for Trump-Vance), including purple Bucks County, where a legal challenge has already been filed by Trump’s campaign.

In the last two presidential elections, Democrats have maintained their strong advantage in Philadelphia — where the party outnumbers the GOP 7-1 — but Republicans have made some progress in the city as the Democratic Party finds increasing support in the Philadelphia suburbs.

Here’s how voter trends have played out in the Philadelphia area in years past and what that could mean for Tuesday.

Philadelphia, historically a Democratic stronghold, helped President Joe Biden win Pennsylvania in 2020, but since his victory four years ago, Democrats have shed approximately 55,000 registered voters in the city. Meanwhile, Republicans have added roughly 4,000 registered voters.

In recent years, some working-class voters in Philadelphia, once a key demographic for the Democratic Party, have shifted to the GOP, with many blaming Democrats for rising prices over the last several years. Democrats’ voter registration advantage peaked in 2016 with a little more than 853,000 registered.

Though registered Democrats far outweigh Republican registration in the city, both parties will look to Nov. 5 and the days after to see how the GOP’s registration additions affected both Harris’ and Trump’s margins.

Democrats have voiced concern about turnout in Philadelphia, but in 2020 Biden received more than 600,000 votes in the city, the largest portion since former President Lyndon B. Johnson in 1964.

Still, Trump did increase GOP totals in 2016 by approximately 12,000, and he received nearly 24,000 more in 2020.

In 2024, Republicans have been paying more attention to Philadelphia than in years past, exemplified by Trump’s first-ever Philly rally in June and his campaign’s local office and deployment of door-knocking and pro-Trump mailers in Democratic-majority neighborhoods.

And Democrats, who have continued to cater to their base in the city — in the face of worries about the Harris campaign’s Philly reach — will look to see if the vice president builds on Biden’s hefty totals.

Despite Biden’s significant vote haul in 2020 in Philadelphia, the city’s portion of the Democratic vote statewide fell from 20% in 2016 to 17.5% in 2020, thanks to an increase in Democratic shares of votes in the Philly suburbs.

The Democrats’ share in the suburbs went from 23% in 2012 to about 26% in 2020 as the city’s share declined over the eight years. But that has not stopped Republicans from courting voters in the collar counties or Democrats from continuing to cultivate their base there.

Just a few examples in recent weeks: Trump held a roundtable in Drexel Hill and Harris participated in a CNN town hall in Aston. The former president worked a staged shift at a Feasterville McDonald’s and Harris connected with anti-Trump Republicans in Washington Crossing.

Democratic candidates dominated Republicans in Philadelphia by an increasing amount between 1992 and 2012. But in 2016, Trump trimmed that margin by 17,000 votes, a key factor in his Pennsylvania victory eight years ago, when he won the commonwealth by 44,000 votes.

In 2020, Trump knocked down the Democrats’ margin in Philly by roughly 4,000 votes, but Biden’s margins elsewhere in Pennsylvania aided the then-Democratic nominee’s win.

On Nov. 5 and the days after, pundits and politicos will look to see what impact Trump makes in Philadelphia, especially as his campaign looks to help Trump lose in Philadelphia by a little less, and if Harris supplements any gains with her own additions in other areas of the state.

Despite his gains in vote totals in Philly, Biden’s margins in 2020 in the city dropped slightly compared with Clinton’s in 2016, and Trump added to his advantage outside of Philadelphia and Pittsburgh areas.

But Biden recaptured Pennsylvania in 2020 by extending the Democratic lead in the Philly suburbs by 105,000 votes compared with 2016 and increased his lead in Allegheny County.

The Harris campaign will look to meet or build on Biden’s success in 2020, as both the vice president’s campaign and the Trump campaign vie for critical Pennsylvania.