By Patrick Ruffini
Graphics by Quoctrung Bui and Aileen Clarke

Patrick Ruffini is a pollster at Echelon Insights.

In almost every presidential battleground state, polling suggests something close to a dead heat between Kamala Harris and Donald Trump. In these states, there are key geographic voting blocs that could determine the outcome.

The best way to tell how a state will vote is to build from the precinct level up, to dig into neighborhood data and to look at the differences in demographics and voting patterns across those precincts. Using this approach, I assembled more than 100 political microcommunities in the battleground states.

Think of them as pieces of a puzzle representing distinct political and social trends that can help us understand the 2024 election. For Ms. Harris and Mr. Trump, each could be a crucial building block in a winning swing-state coalition.

I selected four states that offer a regional and demographic variety of the precinct-cluster puzzle pieces. Within each, there are opportunities for both candidates.

The Keystone State is a cornerstone of the Democrats’ so-called blue wall. According to Nate Silver’s 2024 forecast, the candidate who wins here wins the election 90 percent of the time.

Pennsylvania is a state of contrasts, from the Philadelphia megalopolis to old industrial cities and large swaths of Appalachia. Of all the battlegrounds, urban-rural polarization is starkest in Pennsylvania.

The polarization calculus favored Mr. Trump in 2016, as mostly rural blue-collar white voters moved right faster than suburban professionals moved left and minority Democratic turnout in Philadelphia proper dropped. But the math flipped to favor Joe Biden in 2020, as he made substantial gains in Philadelphia’s suburbs and did better even in blue-collar........

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