On Election Eve, Harris and Trump hold dueling rallies in the biggest of the battlegrounds

"We need you to vote, Pennsylvania.  We need you to vote," Harris emphasized as she spoke to a large crowd in the Keystone State's capital city - Harrisburg - last week. "No one can sit on the sidelines."

Trump's message to his supporters: "Pennsylvania, go vote."

It is no surprise that both major party nominees are heavily concentrating their final campaign schedules in Pennsylvania.

"Pennsylvania is the one state that it's hard to see someone losing and then still winning the presidential race," Mark Harris, a Pittsburgh-based longtime Republican national strategist and ad maker, told Fox News. "It's clearly ground zero."

Harris, a veteran of multiple GOP presidential campaigns, called Pennsylvania "a big tipping point state." 

Pointing to the state's major cities - Philadelphia and Pittsburgh - its electorally crucial suburban areas, and its vast swath of rural counties, Harris highlighted, "I think it's a good microcosm of America."

The former president, the current vice president and their running mates - GOP vice presidential nominee Sen. JD Vance and his Democratic counterpart - Minnesota Gov. Tim Walz - as well as top surrogates, have repeatedly stopped in the state this summer and autumn.

While the campaigns and their allied super PACs have poured resources into all seven battlegrounds, more money has been spent on running spots in Pennsylvania than any of the other swing states, according to figures from AdImpact, a top national ad tracking firm.

Pennsylvania, along with Michigan and Wisconsin, are the three Rust Belt states that make up the Democrats' so-called "Blue Wall."

The party reliably won all three states for a quarter-century before Trump narrowly captured them in the 2016 election to win the White House.

Four years later, in 2020, Biden carried all three states by razor-thin margins to put them back in the Democrats' column and defeated Trump.

A New York Times/Siena College poll in Pennsylvania last Tuesday through Saturday and released on Sunday indicated Harris and Trump deadlocked at 48% among likely voters in the state. It was the latest survey to indicate a tied or margin-of-error race. 

Senior Harris campaign officials, taking questions from reporters on Sunday evening, noted that roughly three-quarters of Keystone State voters will cast ballots on Tuesday "because unlike other states, the guidelines, and availability of early voting is just more limited in Pennsylvania."

However, they added that when it comes to the early vote in the state, "we really like what we're seeing."

They predicted that "we expect in Pennsylvania, we'll have a very strong Election Day."

However, Pennsylvania is also the state where Trump survived an assassination attempt in July - two days before the start of the Republican National Convention. Additionally, the former president returned to the site in Butler - in the western part of the state - for a massive rally last month.

Ahead of his two rallies in Pennsylvania, Trump kicks off his Monday campaign schedule in North Carolina, where he will hold his fourth rally since Saturday, which has raised eyebrows among political operatives.

"We've had a lot of luck in North Carolina. We won it twice," Trump said Sunday in Kinston. "We are going to win North Carolina."

A day earlier, at another North Carolina rally, he warned his supporters that "when you're winning by a lot, you can still lose by a little."

Polls indicate a margin-of-error race in North Carolina, the only one of the seven key battlegrounds that Trump narrowly carried over Biden four years ago. A source in the former president's political orbit confided to Fox News that there were concerns of a possible setback in the Tar Heel state.

While Harris closes out her campaign with a late night rally in Philadelphia, Trump will be in Grand Rapids, Michigan, for his final rally. For Trump, it is tradition. He closed out his 2016 and 2020 campaigns in the southwestern Michigan city.

Trump, as he has in recent days, on Sunday once again argued without providing proof that the Democrats were trying to cheat.

"They are fighting so hard to steal this damn thing," the former president charged at his Pennsylvania rally.

Later, at his rally in North Carolina, he also reiterated his claim that "we have a big lead. We have a big lead. The fake news, they don't tell you this. We have a big, beautiful lead."

Responding, Harris told reporters on Sunday that "I would ask in particular people who have not yet voted to not fall for his tactic, which I think includes suggesting to people that if they vote, their vote won't matter. Suggesting to people that somehow the integrity of our voting system is not intact so that they don't vote."

"It is meant to distract from the fact that we have and support free and fair elections in our country," Harris argued. "We did in 2020. He lost."

The Harris campaign on Sunday night also touted its very formidable get-out-the-vote operation, highlighting that it had more than 90,000 volunteers over the weekend helping to turn out voters, and that they knocked on more than three million doors in the key battlegrounds.