PITTSBURGH, PA - Vice President Kamala Harris and running mate Minnesota Gov. Tim Walz barnstorm through western Pennsylvania on Sunday, on the eve of the kickoff of the Democratic National Convention.

Hours earlier, former President Trump declared "I love Pennsylvania" as he held a rally at an indoor arena in Wilkes-Barre, in the northeast corner of the Keystone State.

Pennsylvania has been and will continue to see plenty of campaign trail traffic. With 19 electoral votes up for grabs, it's the largest prize among the seven battleground states that will likely decide the outcome of the presidential election.

"We're winning by a lot in Pennsylvania," Trump declared on Saturday. 

TRUMP RUNNING MATE VANCE AIMS TO TURN BLUE WALL STATES RED

Donald Trump

Former President Trump pumps his fist after speaking during a campaign rally at Mohegan Sun Arena at Casey Plaza on Aug. 17, 2024, in Wilkes-Barre, Pennsylvania. (Michael M. Santiago/Getty Images)

But an average of all the polls conducted in Pennsylvania since Harris replaced President Biden at the top of the Democrats' 2024 ticket four weeks ago indicates it is all tied up.

And both campaigns have been placing plenty of emphasis on the Keystone State.

Harris made Philadelphia her first stop of her first battleground state swing after announcing Walz as her running mate.

Vice President Kamala Harris (right) and her running mate, Minnesota Gov. Tim Walz, speak in front of a large crowd in Philadelphia, Pennsylvania, on August 6, 2024, as they kick off a battleground state campaign swing 

Vice President Kamala Harris (right) and her running mate, Minnesota Gov. Tim Walz, speak in front of a large crowd in Philadelphia, Pennsylvania, on August 6, 2024, as they kick off a battleground state campaign swing  (Fox News - Paul Steinhauser)

And Trump and his running mate, Sen. JD Vance of Ohio, both return to Pennsylvania on Monday for separate events focused on the economy.

HARRIS AND TRUMP TRADE FIRE IN BATTLE FOR THE BLUE WALL STATES 

Pennsylvania, along with Michigan and Wisconsin, make up what's known as the Democrats' ‘blue wall,’ which the party reliably won in presidential elections for a quarter-century before Trump narrowly carried all three states in 2016 en route to winning the White House.

But four years later, in 2020, Biden won back all three by razor-thin margins, to defeat Trump and claim the presidency.

Kamala Harris and Donald Trump

Both campaigns have invested heavily in Pennsylvania, spending big bucks on ads and outreach. (Getty Images)

On Sunday, Harris and Walz will be accompanied by their spouses, second gentleman Doug Emhoff and Minnesota first lady Gwen Walz. The bus tour will depart from Pittsburgh's airport and make stops, according to the Harris campaign, in Allegheny and Beaver counties, which are considered swing areas in the battleground state.

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Both campaigns have invested heavily in Pennsylvania, spending big bucks on ads and outreach.

Harris Walz bus in Pittsburgh

The campaign bus for Vice President Kamala Harris and Minnesota Gov. Tim Walz at Pittsburgh International Airport in Pennsylvania, Aug. 19, 2024. (Fox News - Paul Steinhauser)

But the Harris campaign touts that their grassroots outreach and get-out-the-vote infrastructure – with 36 coordinated offices in conjunction with the Democratic National Committee and the state party – dwarfs the presence of the Trump-Vance campaign in Pennsylvania.

Pennsylvania will not only see plenty of stops by the candidates between now and November, it will also be the site of what's likely to be the first and possibly only debate between Harris and Trump, which is scheduled to be held at the National Constitution Center in Philadelphia on Sept. 10.

Get the latest updates from the 2024 campaign trail, exclusive interviews and more at our Fox News Digital election hub.