Hillary has won PA — but everyone’s still holding their breath, because it’s all about the margin.

As the results from the Pennsylvania primary trickle in, the Obama camp has been busily pre-spinning, acknowledging that he won’t win, but suggesting that if Clinton wins anything under double digit figures, she won’t have enough popular support to swing the superdelegates.

Meanwhile the victorious Clinton camp is asking the question, with all the money and campaign time that Obama has spent in Pennsylvania, why shouldn’t he win? And doesn’t that suggest he’ll have a problem with white working class folks in the general election?

So the two things to watch for in the blizzard of number crunching — how much does Hillary win by, and which way will the nervously sweating superdelegates swing?

What to look for as the results trickle in: Check for turnout at 1 p.m. By this point Tuesday, the campaigns should have a good sense of what kind of outcome to expect. They will look first to Philadelphia, where a crush of voters early in the day will bode well for Obama and badly for Clinton since it will signal that he could win the big margin he needs to take out of the city. Plus, African Americans tend to go to the polls later in the day in Philadelphia, according to a city-based Democratic strategist, which means Obama can expect a late surge from voters who support him in disproportionately high numbers. Don’t be fooled by early results. The cities and suburbs usually report their returns first, which gives the candidate favored in those areas a quick – and sometimes fleeting – lead. The conservative-leaning small towns through the center of the state usually filter in much later in the evening. — Politico

It’s all about the margin: A double-digit Clinton victory is possible, but only a couple of polls indicate that’s likely. The latest Newsmax/Zogby poll shows her ahead by a 51% to 41% margin. In a poll conduced April 19 and 20, Suffolk University in Boston predicted a Clinton victory by 52% to 42%. Yet the rest of the spreads remain in the middle single digits. That means Pennsylvania’s 188 delegates will likely be pretty much evenly split, with Clinton gaining a little ground on Obama, but not much. — MarketWatch

Ignore the exit polls: … I see them as rough estimates of how various demographics are voting. They might even be a little fun, a great way to pass time the last couple of hours before the polls close. But they are not predictive, they are not decisive, and eventually they get cleaned up with real data after all the votes have been counted. — Daily Kos

A potted history of PA: At the borders of the state where Hillary Clinton and Barack Obama have waged what could be the ultimate contest of their seemingly endless 2008 marathon, there should be signs: “WELCOME TO PENNSYLVANIA — YOU ARE NOW IN THE 19TH CENTURY.” Call it the Retro State, trapped in amber between the Civil War and the 1960s civil rights revolt, which it managed to ignore. The irony of today’s Pennsylvania primary is that the historic race and gender confrontation between Obama and Clinton is being staged in one of the most reluctant states to elect a woman or African-American to major office. Until now, that has been the only way to win big in Pennsylvania — be male and pale. — USA Today

The four voting blocs to watch: Four groups of voters — working-class males, young people, rural and small-town Americans and Hispanics — stand out as the key pieces of that puzzle. All four groups are in flux, and they will provide the leading indicators of where the race is heading. The role of these key voting blocs will be much in evidence in Pennsylvania, a state that in many ways is a microcosm of the U.S. — Gerald F Seib, Wall Street Journal

Do your own sums on the delegate calculator: CNN Delegate Calculator

Spinning the results: This morning the New York senator told reporters any win should be considered a victory given Barack Obama’s spending advantage. In case she wasn’t clear enough, the campaign followed up with its strongly worded memo. “The Obama campaign is attempting to pre-spin the results from tonight’s Pennsylvania primary by suggesting that Sen. Clinton should–and will–win,” the Clinton memo says. “But after the Obama campaign’s ‘go-for-broke’ Pennsylvania strategy, after their avalanche of negative ads, negative mailers and negative attacks against Sen. Clinton, after their record-breaking spending in the state, a fundamental question must be asked: Why shouldn’t Sen. Obama win?” – Suzanne Smalley, Newsweek

Bill’s back: In a radio interview posted Monday, Bill Clinton claimed that Barack Obama’s campaign has “played the race card on me.”…At the very end of the interview, when Bill thinks he is no longer on the line, you can hear him saying, “I don’t think I should take any sh-t from anybody on that, do you?” — The Huffington Post

Obama’s got new superdelegates: Obama strategists said Monday that they expected to announce a series of additional endorsements by uncommitted superdelegates shortly after Pennsylvania votes. A strong showing by Obama in Pennsylvania would give superdelegates more comfort in coming forward, but a bad loss might send them back to the assessment stage. — The LA Times

Pennsylvania? Whatever: Pennsylvania result – is it meaningless? In general, I think the coverage of Pennsylvania is wildly overblown. What happens tonight is not going to effect the outcome of the nomination. Obama will be the nominee, and the only thing that could stop him would be a massive scandal. If Wright and Bittergate couldn’t dent his standing, a loss in Pennsylvania won’t, either. The only thing the Pennsylvania results could possibly change is the timing of Clinton’s departure, and even that won’t happen unless Obama somehow pulls off a shocker upset win. – Jonathan Chait, The New Republic

White guys rule again: Hillary Clinton’s release Monday of her first Osama bin Laden ad sets the stage for a general contest that Republicans could only dream about: an election fought over issues of patriotism, 1960s radicalism, liberal elites, gun control, terrorist threats, intimidation by a black preacher, and a 3AM phone call signaling enemy attack. With the bin Laden spot, Clinton has set the stage for an election in which a crucial voting block will once again be white men… — Thomas B Edsall, The Huffington Post

A pledged delegate asks — can I change my mind?: My name is on the Pennsylvania primary ballot as a delegate candidate pledged to Barack Obama. I will be competing for one of six delegate spots allotted to my congressional division, the 6th District. It’s a gerrymandered swing district composed of wealthy Philly suburbs, Amish farm country, and the diverse cities of Norristown, Pottstown, and Reading. The vote at the top of the ticket on April 22 will determine how many delegates Clinton and Obama win here. — Slate

Delegate count will take time: Don’t expect the full picture until at least Wednesday. There are 158 pledged delegates up for grabs. They are awarded proportionately by congressional district; if a candidate wins 58 percent of the popular vote in a district, he or she gets 58 percent of the delegates. But counting them is not that simple. For one thing, the popular vote is tallied by county, but some congressional districts overlap several counties. Elections officials say their spreadsheets are not set up to calculate the delegates automatically. So bear with them! — The Caucus blog, NY Times