The candidate who burst onto the national stage promising to bring red and blue states together is suddenly looking quite blue.
Sen. Barack Obama's second consecutive lopsided loss in a critical swing state has exposed soft spots in the support he's been able to secure.
While Obama remains the prohibitive front-runner -- with an effectively insurmountable lead in elected delegates -- those potential weaknesses among key demographic groups are fueling a fierce argument inside the Democratic Party over Obama's ability to win a general election.
The weaknesses constitute Sen. Hillary Clinton's last best shot at the nomination: convincing party insiders who serve as superdelegates that Clinton can turn out the voters who are critical to the Democrats' chances against Sen. John McCain, R-Ariz.
"The bar was set high in Pennsylvania and she got over it with room to spare," said Steve Grossman, a former Democratic National Committee chairman who is helping the Clinton campaign lobby superdelegates. "She's been able to build a broader coalition in each of the last three primaries. And I think that his [Obama's] coalition is more available to her than hers is to him."
Despite being badly outspent by Obama, the New York senator won a resounding, nearly 10-point victory in Pennsylvania on Tuesday.
It was a statewide Obama wipeout: He carried only seven of the state's 67 counties, primarily in the Philadelphia and Harrisburg areas in the southeastern portion of the state.
"In the big states that count -- that we must carry to win the Electoral College -- she's the best candidate," Pennsylvania Gov. Ed Rendell, a Democrat, said on a conference call with reporters Wednesday. "It was a victory virtually everywhere in the state. … This was an awesome victory, a landslide."
Clinton started making that argument to superdelegates in the immediate aftermath of the primary.
"Last night's win should give a lot of fresh information to our superdelegates," Clinton said Wednesday on ABC's "Good Morning America". "Because, after all, the road to Pennsylvania Avenue does lead through Pennsylvania. And the big win that I had, the broad base of coalition that I put together, is exactly what we're going to need to have in the fall. And, in fact, that's what I've done, in big states, in swing states since this process began."
According to exit polls, Clinton carried 54 percent of voters earning less than $50,000 a year; 62 percent of Democrats who don't have college degrees; 63 percent of voters older than 65; and 66 percent of white women.
Clinton ran up similarly wide margins among those demographic groups in Ohio six weeks earlier.
Both states are key to Democrats' November chances; Al Gore and John Kerry both narrowly carried Pennsylvania, and both men would have won their races if they had won Ohio as well.
In one particularly troublesome sign for the fall, only 50 percent of Pennsylvania voters who voted for Clinton said they would definitely vote for Obama if he was the Democratic nominee, according to exit polls.
Twenty-six percent said they would cross party lines and vote for McCain.
Obama aides dismissed such numbers as skewed given the intensity of the primary campaign.