A few weeks ago, though it feels like months, exhausted campaign staffers and reporters amused themselves with gallows humor about the Pennsylvania Scenario -- a wildly improbable convergence of circumstances that would extend a race that was supposed to be over by winter deep into the spring with a dramatic showdown in the last big state on this year's Democratic calendar.
Now, the Pennsylvania scenario is here.
The campaigns of both Senator and Senator wake up this morning to a seven-week stretch that includes just three contests, and climaxes on April 22 in Harrisburg.
"Pennsylvania is the new Iowa," said Clinton spokesman Doug Hattaway.
The campaigns bring their well-known strengths and weaknesses to Pennsylvania: Obama will likely have the momentum of two friendly, smaller contests this month in Wyoming and Mississippi, and a formidable lead among the pledged delegates chosen in primaries and caucuses, one that even a defeat in Pennsylvania won't erase. He will also arrive with solid support from African-American, well-educated, and younger voters.
But Clinton will bring a proven resilience, the support of the local political establishment, and a message that played well in the industrial Midwest of Ohio -- a state parts of Pennsylvania closely resemble.
The seven weeks leading to Pennsylvania will give breathing room to new stories and storylines. They'll include the Chicago corruption trial of Obama's former patron, Tony Rezko. They appear likely to include the release of Clinton's tax returns and her White House schedule. And if the local mores kept the race relatively genteel in Iowa, Philadelphia is known for no such compunction. Instead, Pennsylvania seems likely to be the theater for a grinding, drawn-out and increasingly bitter conflict.
Obama has seen that Clinton scorns his campaign's insistence that she simply can't win, and that to win, he'll need to shove her off the stage.
"We have not hesitated to draw distinctions between the candidates and we'll continue to do that," said Obama's chief strategist, David Axelrod. "If Sen. Clinton wants to take the debate to various places, we'll join that debate. We'll do it on our terms and in our own way but if she wants to make issues like ethics and disclosure and law firms and real estate deals and all that stuff issues, as I've said before I don't know why they'd want to go there, but I guess that's where they'll take the race."
In his San Antonio concession speech, Obama maintained the pose of a frontrunner, echoing aides' case that pledged delegates are the only meaningful measure of victory -- though he, too, will have to rely on the support of superdelegates to secure victory.
"No matter what happens tonight, we have nearly the same delegate lead as we did this morning, and we are on our way to winning this nomination," he said. Obama also sought to keep his sights on the presumptive Republican nominee, Senator , and to link Clinton and McCain as the faces of the status quo.
"John McCain and Senator Clinton echo each other in dismissing this call for change," Obama said.
As the results from Ohio came in, Obama's aides adopted the guerilla tactics of an insurgent, as his campaign counsel called, uninvited, into a Clinton campaign conference call, to berate Clinton aides about their disrespect for caucuses.
Clinton, too, is steering a course for sharpening conflict. If she has a path to victory at the Democratic National Convention in August, that path runs straight through Obama. Even under the most optimistic scenarios, she will trail among the delegates chosen by voters and caucus-goers. So she will have to prove to the party leaders known as superdelegates not just that she's a qualified contender -- but also that Obama is so weak, so risky, that the typically cautious superdelegates should overrule the pledged delegates.
Clinton's lesson from Ohio and Texas is clear: attacking Barack Obama directly works. Five days before the primary, she attacked his fitness to serve as Commander-in-Chief in a television advertisement depicting a late-night crisis at the White House. In the same short period she attacked his credibility on promises to rein in free trade. And she beat him almost two-to-one among voters who decided in the last three days of the race, a group Obama has dominated in past votes.
"Together we will turn promises into actions, words into solutions, and hope into reality," Clinton said in her victory speech in Columbus, drawing tacit contrasts with Obama.
Clinton stressed that she'd won states like Ohio, crucial to the general election, and her aides began an argument that they will need to win with the Democratic Party's elite: That Obama can't be trusted to win.
She also signaled that she's headed into another bitter procedural battle: The fight to count the votes in Florida, where no Democrats campaigned, and Michigan, where Clinton was the only leading Democrat even on the ballot.
"We've won Florida, Nevada, New Mexico, Arizona, Michigan, New Hampshire, Arkansas, California, New York, Massachusetts, Oklahoma, Tennessee, and today we won Rhode Island," she said in Columbus, including the two states in question in her list of victories.
Carrie Budoff Brown contributed from San Antonio.
By Ben Smith