Since the last time Barack Obama had to face a Republican opponent in Pennsylvania, the political battleground of the nation's sixth-largest state has changed a bit.

Unemployment is up; jobs are down. The voting-age population may be slightly older, with more baby boomers in or near retirement. And Republicans have slightly narrowed the Democrats' voter-registration advantage.

Some of the changes are subtle, and they don't all favor one party or the other. Analysts said it was hard to predict how they could affect the Nov. 6 election.

The economic trends, as in other states, would seem to trigger anger within the electorate and hurt the party in the White House.

Yet, an Inquirer poll Sept. 9-12 found Obama leading Mitt Romney in the state by about the same margin (11 points) by which he beat John McCain in 2008. A poll released Tuesday by Muhlenberg College assessed the gap at 9 points. The state GOP said Thursday that it had a survey showing a one-point race.

Since Obama took office in January 2009, the number of Pennsylvanians holding a job has dropped 76,000. The unemployment rate, while below the national average, has jumped from 6.8 percent of the available workforce to 8.1 percent and was up in August. The number of Pennsylvanians living in poverty had gone up 12 percent at the close of 2011.

The Appalachian Mountains, which spread across the Keystone State in a long, green arc, separate what, over many years, are becoming two different Pennsylvanias.

Counties west and north of the mountains, while becoming more Republican, generally are declining in population. Many regions east and south of the ridges are more Democratic - and growing.

In the west, the economy is more dependent than in other areas on manufacturing, one of the hardest-hit economic sectors in the last four years. The state has lost 40,000 manufacturing jobs.

"I think you're seeing a continuation of a trend that began with 1980; actually, I think our high-water mark was in the '40s," said Richard L. Palilla, executive director of the Indiana County Planning Commission in Western Pennsylvania.

The loss of manufacturing has been at least partly offset by the big increase in gas drilling that has occurred in the Marcellus Shale since 2008.

"All politics is local, and this Marcellus Shale has had a definite impact on the economy of southwestern Pennsylvania," said George Vitteck, Democratic chairman of Washington County. "What effect that's going to have [on politics], I don't know."

The 2010 census found a slight increase in the minority population in Pennsylvania, mostly in the east - a trend that may be continuing, particularly among Hispanics in the Reading-Harrisburg-Allentown crescent.

But many Hispanics are not eligible to vote, and some new arrivals are illegal immigrants, "so I'm not sure that would have changed anything about the electorate," said Gordon De Jong, professor of sociology and demography at Pennsylvania State University.

Pennsylvania, for decades, has been among the nation's slowest-growing states. Between 2008 and 2011, the population grew 2.4 percent, according to census estimates - from 12,448,279 to 12,742,886.

The relatively small numbers of people moving into the state often come from the more heavily Democratic states of neighboring New Jersey and Maryland.

Sue Williams, former Republican chairwoman of Adams County, said: "Maryland is a very liberal state. . . . They have migrated here with the hopes of a lesser tax burden, but once they get here, they want the handouts they had in Maryland."

More than elsewhere, the Poconos have been transformed by in-migration. Monroe County grew 22.5 percent from 2000 to 2010, Pike County 24 percent.

But from 2010 to 2011, the population in each county dipped a tiny bit, the Census Bureau found.

"We had fantastic growth in the early 2000s, especially after Sept. 11," said Tom Geffers, Monroe County GOP chairman. "But since the recession of 2007 to 2008, a lot of people have gone back to New York and New Jersey. We have one of the highest foreclosure rates in the state."

The number of Democratic voters in Monroe County has declined a little. But the number of Republicans is down, too.

In fact, voter registration is down across the state, a reflection of lesser interest in this year's election.

Interest in 2008 was fanned by millions of dollars in TV advertising and a sense that results in Pennsylvania were crucial to the national outcome.

This fall, so far, Obama and Romney are largely ignoring Pennsylvania in both advertising and personal appearances. The reason, apparently, is Obama's large lead in most polls.

Across Pennsylvania, the number of registered voters has declined 5 percent since 2008. Many people who registered in the 2008 excitement have not voted since and have had their names cleaned from the rolls.

The Democrats, with 4.48 million registered voters in 2008, had slipped to 4.16 million as of Sept. 10, with four weeks left in the registration period. That was a drop of 314,000, or 7 percent.

The Republicans, who had 3.24 million registrants in 2008, had dropped to 3.09 million. That was a decline of 154,000, just over 4.5 percent.

The only category of voters that had increased was independents - up 21,000, or 2 percent. Independents typically are swing voters.

Polls consistently show that Obama's strength is overwhelmingly in Philadelphia, which in 2008 gave him 83 percent of its vote.

But the key to the election may be in the Philadelphia suburbs, where Democrats since 2008 have gained control of the Montgomery County Courthouse and have made inroads on traditional GOP power elsewhere.

Republican registration is down slightly in all four suburban counties: Bucks, Chester, Delaware, and Montgomery.

Democrats are down in all but Chester County.

All four suburban counties voted for Obama in 2008.

Have there been other changes to Pennsylvania since 2008?

Certainly, the number of baby boomers in or near their 60s has increased.

These voters could be more worried about the future stability of Social Security and Medicare. But will they, as older voters in the past, trust Democrats more on these issues? Time will tell.

In terms of election success, the last four years have been a banner era for Pennsylvania Republicans.

The GOP has captured the governor's office and taken control of the state House to go with the Senate. It has picked up a solid majority of the state's 19 U.S. House seats. It now controls top offices in four-fifths of county courthouses.

Robert Gleason, the Republican state chairman, said he saw no reason the Republicans gains should not continue.

But the trend indicators are like a child's drawing. The lines are crooked and go every which way.

"Several of the demographic trends are in a direction that benefits the Democratic positions," said De Jong, the Penn State professor.

"Unemployment - that begins to go in the other direction, so there are counter-trends as well," he added. "I don't know how they add up."