LANGHORNE, Pa. – From the 1930s through the 1950s, Bucks County northeast of Philadelphia acquired a glamorous reputation as a retreat for Manhattan celebrities, including Oscar Hammerstein, who, according to local legend, was inspired by the view from his Doylestown front porch to write “Oh, What a Beautiful Mornin’,” the opening song of “Oklahoma!” Today the county, which is 93 percent of Pennsylvania’s 8th Congressional District, figures in Republicans’ plans to sing that song on the morning of Nov. 3.

The district has about 209,000 Democrats, 189,000 Republicans and 66,000 independents. The seat is held by a Democrat, Patrick Murphy, 36, the first Iraq War veteran to serve in Congress. He was elected in 2006 when he defeated the one-term Republican incumbent, Mike Fitzpatrick, 47, an attorney, who is Murphy’s opponent again this year.

More than half of the 7 percent of the district that is not in Bucks County is in northeast Philadelphia, where a lot of the city’s police and firefighters live – they are required to reside in the city – and many conservative Democrats, too. The remainder of the district is in suburban Montgomery County. Lower Bucks County is primarily blue collar, the upper county is agricultural and the central portion is an upper-income bedroom community for Philadelphia.

Fitzpatrick, who had been a Bucks County commissioner for 10 years, won in 2004, a good Republican year. He lost in the Republicans’ annus horribilis of 2006, when they suffered the first of two consecutive wave elections. (In a wave, a party gains or loses a net of at least 20 seats in the House of Representatives.) The Democrats’ 2006 candidate for governor was Ed Rendell, the former Philadelphia mayor who was much loved in the suburbs for making the central city – he was called the “mayor from Pine to Vine,” two downtown streets – safe for them to go in for meals and entertainment. Rendell defeated his Republican opponent in the 8th District by 40 points. So, 2006 was a Republican nightmare: Incumbent U.S. Sen. Rick Santorum lost the district by 20 percent.

Still, Fitzpatrick lost by just 1,518 votes out of 249,817 cast, and he carried the Bucks County portion of the district. He did not attempt a comeback in 2008 because he was receiving chemotherapy and radiation for colon cancer. He is now well.

Although Bill Clinton campaigned for Murphy in 2006, perhaps with his wife’s 2008 presidential candidacy in mind, Murphy became the first Pennsylvanian holding federal office to endorse Barack Obama’s candidacy. Today, the Clinton-Obama contest still reverberates.

Political analyst Charles Cook doesn’t hire dummies, and one of his talented associates, David Wasserman, has this theory: Democratic members of Congress who are in peril are disproportionately from districts where Democrats preferred Hillary Clinton over Barack Obama in 2008. She decisively beat Obama in the 8th District with 63 percent, and in November 2008 her voters were not Obama swooners: They simply hired him to fix the economy.

Murphy has voted with Speaker Nancy Pelosi 97 percent of the time, including on the stimulus, health care, cash for clunkers, the cap-and-trade climate legislation and organized labor’s priority, “card check,” which would abolish workers’ rights to secret ballot elections in workplace unionization decisions. Fitzpatrick is a centrist in a Republican Party where the center is migrating to the right. He favors extending all the Bush tax cuts and rescinding to the Treasury all unspent TARP and stimulus funds.

The 8th is a swing district that should swing in a year like this. Polls indicate, however, that the race is not yet settled.

Fitzpatrick says that although he was his family’s first Republican, his seven siblings have all seen the light. He and they grew up in the 8th District, in Levittown, one of the instant suburbs (the first, also called Levittown, is on Long Island) that were mass produced after World War II by William Levitt. They were incubators of the postwar middle class, many of whose members’ bought their first homes from Levitt for $7,990.

Bucks County is emblematic of not only 20th-century America, but 18th-century America, too. It was from the Bucks County bank of the Delaware River that George Washington, on Christmas night, 1776, launched the boats that carried the attackers that surprised the Hessians in Trenton. Republicans hope that on Nov. 2 a piece of another, if rather less momentous, moment in America’s political evolution will occur.

© 2010, Washington Post Writers Group