It's why both Kamala Harris' and Donald Trump's presidential campaigns have ramped up efforts on the ground in Pennsylvania.
"It's a tight race in Pennsylvania, it's really come down now to people going door-to-door," said Michael Kozak, an assistant professor at Drexel University.
Vice President Harris' team says they knocked on more than 100,000 doors in Pennsylvania this weekend.
"Our volunteers are prepared and ready to answer those questions and it's made a difference," said Lisa-Renee Dumas, lead volunteer with the Harris campaign. "People are opening their doors. They're asking questions."
Former President Trump's team says they're also covering the state, but not relying solely on visiting people's homes.
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"We're going after people where they are at, that includes tailgates, community events, parades," said Tommy Pigott, strategic communications director with the Trump campaign.
"There is history here of counties, towns, a whole sections of the state flipping back-and-forth between blue and red," said Kozak of Pennsylvania's reputation as a swing state.
That status is well-earned as the Keystone State has flipped a couple of times in the last four presidential elections.
In 2008, the state voted for the Democratic candidate, and again in 2012. In 2016, though, Pennsylvania flipped in favor of the Republican candidate. The state then went back to blue in 2020.
Within the battleground state are battleground counties. Chester County has a history of flipping as well.
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The county stuck with the state by going blue in 2008; however, in 2012, the county went for the Republican presidential candidate.
In 2016, they switched to the Democratic candidate and stayed blue in 2020.
Residents in Chester County haven't just flipped their votes, they've also flipped their parties.
The 6abc Data Team found that since 2008, just over 19,000 registered Republicans have switched to Democrats. Just under 16,000 Democrats switched to Republican.
The back and forth of votes and parties makes the ground game even more important to each presidential campaign.
"I don't think either party and their teams that are out there canvassing want to take a chance of taking their foot off the gas pedal between now and Election Day," said Kozak.