SWASHINGTON - If Democrats ever hope to take control of the House of Representatives, they will need to win moderate, slightly right-of-center districts like those surrounding Philadelphia.

But races in those suburbs are tilting toward Republicans as the most intense fall campaigning begins, leaving Democrats with a difficult road in districts where they had hoped to gain ground.

Democrats had hoped the retirement of Rep. Jim Gerlach (R., Pa.) in the Chester County-based Sixth District would provide an opportunity, and that Rep. Mike Fitzpatrick (R., Pa.) might be vulnerable in the evenly split Eighth District, based in Bucks County.

But Democrats stubbed their toes in primary season, trail badly in fund-raising and are fighting the downward tug of President Obama's sinking poll numbers.

"Even in a good Democratic year, 'Pennsylvania six' would be exceedingly difficult" for the party to win, David Wasserman of the Cook Political Report, a nonpartisan election handicapping publication, said. "And this isn't a good Democratic year."

Cook has labeled the Bucks- and Chester-based districts as "likely Republican," a change from "lean Republican" earlier in the year. Other analysts have done the same, including the Rothenberg Political Report, which on Friday moved the Bucks race to "safe Republican."

With a House majority out of reach, Democratic energy is focused on keeping the Senate, where the GOP is pressing for a majority.

"The marquee races, where the resources are going, are in the Senate and governors," said Michael Podhorzer, AFL-CIO political director.

The moderate Philadelphia suburbs, critical to control of the House, have been dominated in recent years by the GOP, with help from Republican-led redistricting and geography.

Consider 2012: Pennsylvania's Democratic House candidates won 83,000 more votes than Republicans, Wasserman said. But the GOP still took 13 of the commonwealth's 18 seats.

"That's a function of Democrats simply being too concentrated in Philadelphia and Pittsburgh," Wasserman said.

Locally this year, the Democratic Congressional Campaign Committee (DCCC) has focused on South Jersey, where Republican Rep. Jon Runyan is retiring, and Republican Tom MacArthur is facing Burlington County Freeholder Aimee Belgard. A former North Jersey mayor, MacArthur is slightly favored in a district the GOP usually owns, though Democrats are hopeful after Obama won there twice.

The DCCC has launched two television ads there - but none in Pennsylvania.

Still, both parties have listed the Bucks and Chester County-based races as high priorities.

"Perhaps we're not doing a good enough job campaigning to D.C. prognosticators, but last I checked none of those live in the district," said Democrat Manan Trivedi, the former Navy surgeon running for Gerlach's seat against Chester County Commissioner Ryan Costello.

Trivedi and Kevin Strouse, a former Army Ranger challenging Fitzpatrick in Bucks, both said a Democratic victory in the Pennsylvania governor's race could help them defy the odds.

But even a big win atop the ticket doesn't always translate to other races. In 2012, though Obama, Sen. Bob Casey, and State Attorney General Kathleen Kane scored big Democratic wins, the GOP gained a House seat.

"Particularly down in the Philly burbs, the voters there know how to split their ticket," said G. Terry Madonna, the Franklin and Marshall College pollster.

The Democrats have campaigned as outsiders who would fix Washington's dysfunction and create economic opportunity by investing in infrastructure and holding down student loan rates.

Republicans locally and nationally have focused on sparking the economy by simplifying the tax code and easing regulations on businesses. Fitzpatrick and Costello would both roll back Affordable Care Act requirements they say are stifling hiring.

Strouse, who turns 35 this month, grew up in Delaware County, served in Afghanistan and Iraq, and worked for the Central Intelligence Agency. He moved to Bucks in March 2013 after being recruited by national Democrats.

"People are pretty fed up with our government in general, with our Republican Congress, certainly with the Corbett administration, because all they see is dysfunction and gridlock," said Strouse, of Middletown. "People are looking for an alternative."

Despite DCCC support, Strouse struggled to win the primary, barely edging Bucks businesswoman Shaughnessy Naughton.

Fitzpatrick, 51, is an oft-tested incumbent who lives near the home where he was raised. "I was not recruited by a national party to run for Congress," he said. "I've lived in the community my whole life."

He also had a huge fund-raising edge as of June 30, the latest reporting date: $1.9 million to $268,721 for Strouse, who had to spend heavily to win his primary.

Now in his third term, he is touting independent ratings that place his voting record near dead-center on the House's political spectrum.

Fitzpatrick says this is his last run for Congress - he believes in term limits - presenting an opening for Democrats in 2016.

A strong showing by Strouse on Nov. 4 might set him up for another try in 2016, though Naughton signaled her intention to remain active when she launched a political action committee last week.

Trivedi, 40, is on his third run after twice losing to Gerlach by 14 points. National Democrats had recruited another candidate, but Trivedi prevailed by securing local backing.

"If you want to see different results in Congress, we've got to start sending different types of people there," said Trivedi, a Birdsboro resident who served in Iraq.

As a doctor, Trivedi said, he has the know-how to rein in health costs, and as another Middle East conflict erupts, his campaign is stressing his military experience as a credential his opponent can't match.

Costello, 38, has focused on the economy, and streamlining the tax code for businesses - as well as ending what he calls needless regulations "that stifle needed research and development and hiring."

Democrats have little hope of ousting GOP incumbents Frank LoBiondo, who is favored over lawyer William Hughes Jr. in New Jersey's southernmost district, or Pat Meehan of Delaware County, whose challenger is LaSalle University professor Mary Ellen Balchunis.

"The artful but legal gerrymandering has really protected the Republicans" in the suburbs, Madonna said.

To win there, he said, Democrats will need strong candidates, money, and a national wave.

So far this year, the tide is with Republicans.