Over the past several weeks, both presidential candidates have deployed massive resources in Pennsylvania to keep, or pick up, the state and its 21 electoral votes.
Today, they'll find out if it paid off, and polls and analysts are predicting a win for Democratic nominee Barack Obama - but say it's not a sure thing.
Obama has consistently polled ahead of Republican candidate John McCain, though McCain has said he plans on a comeback win in the state.
On the eve of the election, McCain has failed to garner more than 46 percent support in Pennsylvania in any recent poll, according to Real Clear Politics.
But the Obama campaign has made clear - through voter-registration efforts and a massive grassroots volunteer network - winning the state isn't something to take lightly.
"On election day, the story will be turnout," said Randall Miller, a St. Joseph's University history professor and political analyst. "This is a test of the Democratic Party's organization."
During the Pennsylvania primary in April, Sen. Hillary Clinton routed Obama in the state by 9 percent, even as it seemed Obama would clinch the nomination regardless.
Obama failed to gain the support of many white, working-class voters, who make up a critical part of the state's demographics. This initial weakness for Obama has given hope to McCain.
In the final weeks of the campaign, McCain, vice presidential nominee Alaska Gov. Sarah Palin and former Pennsylvania Gov. Tom Ridge have barnstormed Pennsylvania looking for votes.
"Don't discount [rural] Republicans turning out to vote," said Miller. "Pennsylvanians love retail politics, and McCain is banking on doing better than anticipated in western Pennsylvania."
In the final Quinnipiac University state poll, Obama and McCain split the white vote evenly with 47 percent each. This split leaves Obama in good shape once his overwhelming support from blacks and Hispanics is factored in.
While not spending as much time in the state as McCain, Obama has powerful surrogates in the field- including Clinton, Gov. Ed Rendell, Mayor Michael Nutter and vice-presidential nominee and Scranton native Sen. Joe Biden.
Rendell, at a get-out-the-vote event on campus yesterday, predicted Obama would win the state by 3 to 6 percentage points.
Still, Miller sees a path to victory for McCain.
"The undecided voters at this stage are so because they're unsure about Obama," he said.
Most undecided voters are older, white women, Miller said, many of whom were Clinton's base during the Democratic primary.
McCain recently sent mailings across the state with a photograph of McCain and Clinton together, a sign McCain knows which voters he needs to pull off an upset.
