During his ritual Election Day basketball game Tuesday, Illinois Sen. Barack Obama was driving past a Senate colleague who had backed him in the Pennsylvania primary.

"I fouled him very aggressively," Pennsylvania's Sen. Bob Casey deadpanned yesterday. "It was my way of being part of history."

The Democrats were on opposite sides in that pick-up game, but they were on the same team this year as Mr. Obama rebounded from a major setback in the state's primary to the biggest Pennsylvania win for a Democratic presidential candidate in more than four decades.

On its face, the president-elect's solid victory accelerated and capitalized on long-term trends in a state that has given its electoral votes to the Democrats in five straight elections. He piled up big margins in Philadelphia and its once-reliably Republican suburbs, building a powerful buffer against Arizona Republican Sen. John McCain's inroads in culturally conservative and nominally Democratic counties in the west.

In election after election, as their votes went increasingly to Democratic candidates such as former Vice President Al Gore, Massachusetts Sen. John Kerry, and Gov. Ed Rendell, Republican officials have argued with waning persuasiveness that the voting performance of the eastern bedroom communities were anomalies -- that the next election was the one in which they would return to GOP roots.

Tuesday's results suggest that it might be time to inter that argument. The increasing Democratic competitiveness in suburban communities adjoining the Delaware and Lehigh valleys does not represent a series of exceptions to a long-standing rule. It's the new rule.

Mr. McCain's challenge in the city of Philadelphia was a given. But he placed big investments in campaign treasure and time in those suburbs. His final debate appearance was bracketed by rallies in Montgomery and Chester counties. In the campaign's final week, he was in Bucks and Delaware counties. He lost all of them.

Mr. Obama's margin topped 60 percent in both Delaware and Montgomery counties. That topped the Democrat's share of the vote in Allegheny County.

The Democratic registration tide propelled by Mr. Obama's potent ground game in the state reinforced the Democratic trend in those counties. While trailing Mr. McCain in the center of the state, the Democrat outperformed Mr. Kerry and Mr. Gore in counties such as Lancaster. He won Harrisburg's Dauphin County easily, one more jurisdiction where the registration advantage flipped from GOP to Democratic in the last year.

While the Obama campaign's work reinforced pre-existing trends in favor of Democrats in some parts of the state, Mr. Casey, in a conference call with reporters yesterday, suggested caution in extrapolating long-term trends from Tuesday's numbers. The Obama ground game was so extensive and so unprecedented in this and other states that it raises questions about whether it can be replicated in future contests.

"I was just blown away by the voter contact numbers," Mr. Casey said. "They literally contacted by phone or at the door as many people as voted. No campaign has ever come half that far."

Mr. McCain did have some success in the state's west. He narrowly won counties such as Washington and Beaver that had been in Mr. Kerry's column in 2004. But those gains were dwarfed by Mr. Obama's relative successes elsewhere.

Comparing Tuesday's results to Mr. Obama's drubbing by New York Sen. Hillary Rodham Clinton in the April Democratic primary, John Green, a senior fellow with the Pew Forum's Study of Religion and Politics, said exit polls suggested "John McCain won the white Catholic vote in Pennsylvania, but just barely. … Obama made gains among white Catholics … [in a result] quite different than the primary in Pennsylvania."

Nationally, Mr. Obama lost the white Catholic vote to Mr. McCain, 52 percent to 47 percent, according to Pew's analysis of network exit polls. But that was a 4-point gain for Mr. Obama compared with the last Democratic nominee. Mr. McCain had hoped for much more from the Catholic voters who strongly favored Mrs. Clinton here in April.

The voting results in older, traditionally Democratic and heavily Catholic communities in the state's Northeast showed a still-strong resistance to the Republican campaign for traditionally Democratic votes in the state. Scranton's Lackawanna County gave native son Joe Biden and his partner a whopping margin of 63 percent to 37 percent. They also won neighboring Luzerne County, 54 percent to 45 percent.

Long-term demographic trends beyond the purely political reinforce Democratic hopes about the countervailing trends in the state's politics. The GOP has made gains in traditionally Democratic communities in the west, as the Democrats have incrementally strengthened their position in the East.

Census figures suggest the net effect of those trends could continue to favor the Democrats because their gains are occurring in parts of the state with growing populations.