By Greg Giroux, CQ Staff

CQ Politics Presidential Race Rating: Leans Democratic

Electoral Votes: 21

There are only five Electoral College prizes as big or bigger than Pennsylvania, and Obama is counting on three of them — California, New York and Illinois. McCain is counting on Texas, and both are running hard in Florida and the Keystone State.

Obama begins the fall campaign with at least a slight edge in Pennsylvania, where a drift to the Democratic column is underscored by the party’s nominee having carried the state in each of the past four presidential elections, even if the past two were quite close.

The intensifying Democratic lean of Philadelphia, amplified by the trend to that party in the city’s once strongly Republican suburbs, has more than compensated for some Republican gains in the less populous western part of the state, outside Pittsburgh, that is more blue-collar and socially conservative.

Democratic Gov. Edward G. Rendell , a former Philadelphia mayor, had a dominant showing in the state’s southeastern quadrant in his landslide re-election of 2006. That same year, Democrat Bob Casey did well in the region in easily taking a Senate seat from a strongly conservative Republican, Rick Santorum.

The Republicans’ ability to hold down Obama’s vote in the Philadelphia area and make up the difference elsewhere may be called into question by the setbacks the party suffered in 2006, including not only Santorum’s drubbing but also the loss of four House seats, two in suburban Philadelphia and two others in typically conservative strongholds. That outcome could not have been envisioned by the Pennsylvania Republican legislators who, less than five years earlier, redrew the state congressional map to a seemingly big GOP advantage.

Looking for further gains in the House, Democrats are heavily focused on the Erie-centered district where businesswoman Kathy Dahlkemper is challenging seven-term Republican Phil English , who took an underwhelming 54 percent in 2006 against a poorly funded Democrat. Dahlkemper’s anti-abortion stance is probably a plus in that district, which leans conservative on social issues but has a strain of economic populism. CQ Politics race rating: Leans Republican.

Rep. Jim Gerlach is favored against Democratic businessman Bob Roggio in the suburbs and exurbs west and northwest of Philadelphia, but Gerlach’s centrism has only allowed him to survive by very narrow margins in three straight elections. CQ Politics also rates this race Leans Republican.

The Democrats also have better challengers this cycle than last against Charlie Dent of the Lehigh Valley and Tim Murphy in the state’s southwestern corner outside Pittsburgh, though the incumbents have the edge. Siobhan “Sam” Bennett, a local party activist and former candidate for mayor of Allentown, is challenging Dent, while businessman Steve O’Donnell is taking on Murphy.

Meanwhile, the Republicans are looking to reclaim some of the seats they lost last time. Their best shot appears to be in the northeastern corner, where Democrat Christopher Carney defeated four-term Republican Don Sherwood, who was politically wounded by a sex scandal. But Carney, a military veteran and former counterterrorism adviser to the Pentagon, is no greenhorn, and Republican Chris Hackett, who heads a recruitment and temporary staffing business, is now an underdog. CQ Politics race rating: Leans Democratic.

At the other end of the state, Republican Melissa A. Hart is seeking to reclaim the exurban Pittsburgh seat she lost to Democrat Jason Altmire . But Altmire hasn’t made any real missteps, and his social-issue conservatism matches that of most constituents. This rating is Leans Democratic as well.

A competitive race could emerge in the suburban Philadelphia district where Democrat Patrick J. Murphy is seeking a second term. While the economy’s problems have soared to the top of most voters’ concerns, the Iraq War will be a marquee issue in this race. Murphy is the only current member of Congress who served in Iraq and has a huge fundraising lead over GOP challenger Tom Manion, a retired Marine colonel whose son was killed in the war. Right now, the race is rated Democrat Favored.