Explaining the Electoral College and how battleground Pa. plays crucial role in 2024 election

Candidates have been flooding the Philadelphia region this campaign season, showcasing the importance of battleground Pennsylvania.

Vice President Kamala Harris and former President Donald Trump remain locked in a dead heat in national and battleground state polls, with all eyes on who will clinch the Electoral College.

Live election 2024 updates in the Philadelphia region and the focus on Pennsylvania

Here is what to know about the process before Election Day.

What is the Electoral College?

As laid out in Article II of the Constitution, the president of the United States is elected by the Electoral College -- not the popular vote.

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Under the system, each state is allocated a number of electoral votes determined by the size of its congressional delegation. The states with the largest number of electoral votes include California (54) and Texas (40).

Experts said the founders debated who should be trusted to choose the nation's leader, with some urging Congress or state legislatures to decide and others advocating for a more democratic vote.

"When they designed our system, they came up with the Electoral College not because they thought it was perfect but as a way to get the Constitution passed, and it satisfied the concerns of both the very populous states and lower populous states," Rachael Cobb, a political science professor at Suffolk University, told ABC News.

Though it's not a direct election of the president, they noted.

"It's really 51 separate elections," Barry Burden, the director of the Elections Research Center at the University of Wisconsin-Madison, told ABC News. "Every state and the District of Columbia has its own rules for running the election. Then each state awards its electors separately, and it's up to candidates to win a majority of those electors to be elected president."

How do electors work?

To win the presidential election, a candidate needs to capture 270 of the 538 total electoral votes.

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Many states have a winner-takes-all approach, meaning that whichever candidate wins the most votes statewide receives all its electoral votes. Two states, however, split their electoral votes: Nebraska allocates three of its five electoral votes by district and Maine allocates two of its four votes by district.

Electors are usually selected by the state's political parties.

While the Constitution doesn't bind electors to vote for the winner of the popular vote in their state, many legislatures have laws in place to prevent an elector from rogue -- or what's called a "faithless elector."

In 2020, some Republican allies of Trump tried to submit fake slates of electors to Congress to undermine President Joe Biden's victory. Several people were prosecuted for their role in the scheme.

Why is it so crucial to this election?

Polls ahead of Election Day show a razor-thin race between Harris and Trump.

It will likely all come down to just a handful of swing states: Arizona, Georgia, Michigan, Nevada, North Carolina, Pennsylvania and Wisconsin.

Some of those states were decided by just 10,000 to 20,000 votes in 2020, and the margins are expected to be just as close in 2024.

Pennsylvania is considered crucial to the outcome of the race, as it boasts the most electoral votes (19) of any of the battlegrounds. The state cemented President Joe Biden's victory in 2020, flipping blue after going red for Trump in 2016.

Voter guide 2024: Pennsylvania, New Jersey, Delaware

If Harris wins Pennsylvania along with Michigan, Wisconsin and a single electoral vote in Nebraska (all of which Biden won in 2020) she would reach 270 electoral votes even if she were to lose the remaining four swing states.

If Trump wins Pennsylvania, and holds all the states he won in 2020, he would need to also flip Georgia to win.

What if there is an Electoral College tie?

A 269-269 tie is not outside the realm of possibility, though it's unlikely.

It's happened only once under the current rules of the Electoral College: the 1824 presidential election.

In that case, as the Constitution requires, Congress carried out a "contingent election" to decide the winner. A contingent election requires the House of Representatives to select the winner, with each state having one vote. A candidate would need support from 26 of the 50 states to be elected.

538 has analyzed the different scenarios in which a tie could result between Vice President Harris and former President Trump.

Cobb called the possibility of a tie a "real concern" this year and explained what would likely happen next.

"The House of Representatives is controlled by Republicans and so the likely outcome in this election, should it be a tie and should it go to the House of Representatives, is that the Republican nominee would win," Cobb said.

What about the popular vote?

"It's a symbolic victory to win the popular vote, but it's not required," Burden said. "And twice in the last five elections, we've seen the popular vote go one direction and the Electoral College go the other. That could well happen this time as well."

Candidates who lost the popular vote but won the Electoral College are John Quincy Adams in 1824, Rutherford B. Hayes in 1876, Benjamin Harrison in 1888, George W. Bush in 2000 and Trump in 2016.

After the 2016 election, when Hillary Clinton eclipsed Trump in the popular vote by nearly 3 million but lost the Electoral College, debate sparked about whether the system should change.

Pros and cons of the Electoral College, according to experts

Those in favor of the Electoral College generally note its written into the nation's founding document and has largely worked since then.

"Many aspects of the Constitution have not been changed since 1789 and are still in place. The Electoral College is still mostly operating the way it was originally intended. So why mess with success?" Burden said.

Burden and Cobb noted it also forces campaigns to focus on traveling from state to state to meet voters. Without the need to win electors, presidential contenders would instead likely run a more nationalized campaign and focus on highly-populated cities while ignoring smaller, rural communities.

The main reasoning against the Electoral College is that it means not every vote is equal, as a handful of key swing states usually determine the winner of an election.

"Another argument is that, essentially, it has disproportionate influence," Cobb said. "That smaller states have a disproportionately higher number of electoral votes relative to their population, meaning that individual votes in these states carry more weight than in those larger states."

"The one person, one vote idea has really taken hold in the United States over time, and the Electoral College does not meet that," said Burden. "Votes are unequal. Some voters matter a lot more, and others matter less. And that's inconsistent with really every other kind of election in the United States."

ABC News contributed to this report.