Voters in Pennsylvania rarely elect black and female candidates.

But they'll have to choose one or the other in the April 22 Democratic presidential primary between Sens. Barack Obama and Hillary Rodham Clinton.

There's no consensus explanation among political operatives and scholars for the political glass ceiling in this state, which currently has only one black and one woman in its 21-member congressional delegation and has never had a black or female governor. Only one black and one woman have ever sought the governorship on a major party ticket.

Some chalk it up to the parties' failure to recruit more women and blacks, and a tendency to favor incumbents over untested upstarts. Some theories hold that juggling young families and political careers deters women from seeking full-time office or voters from choosing them. Some believe the concentration of blacks in urban areas works against black candidates for statewide office who must seek votes in predominantly white rural counties once famously compared to Alabama.

Pennsylvania's voting-age population is more than 50 percent female and about 10 percent black, but neither group has comparable representation among top state and federal elective offices. One of the worst showings: Only 15 percent of the 253 seats in the Legislature are filled by women, leaving Pennsylvania 43rd nationally.

State Democratic Party chairman T.J. Rooney sees no ''inherent bias'' against black or female candidates. ''The challenge that confronts candidates of any stripe is being able to put together the money and the organization,'' he said.

But racial bias is still a reality in much of the state, said J. Whyatt Mondesire, state president of the National Association for the Advancement of Colored People. Outside Philadelphia and its suburbs, he pointed out, few minorities hold positions of power in county party organizations.

Recalling that Democratic strategist James Carville once likened Pennsylvania's vast rural center to Alabama, Mondesire said. ''In many parts of the state, it's true.''

Gov. Ed Rendell, who backs Clinton, seemed to agree in February when he said some white Pennsylvanians would likely vote against Obama because he is black. Rendell said racial bias may have contributed 5 percentage points to his own 22-percentage-point victory in 2006 over Republican Lynn Swann, the former Pittsburgh Steelers star who is the only black ever to run for governor for a major party.

When criticized for his remarks, Rendell added that Clinton faces similar obstacles because of her gender.

Rendell said both Clinton and Obama have done a good job overcoming stereotypes and Obama could benefit from his ''ability to bring new voters into the electoral pool.''

Driven by the contest between Clinton and Obama, Democratic registration in the state has soared over 4 million, the first time by any party.

Thaddeus Mathis, co-director of Temple University's Center for African American Research and Public Policy, attributes the paucity of elected blacks to the concentration of the black population in Philadelphia and Pittsburgh.

U.S. Rep. Chaka Fattah, D-Pa., who backs Obama, said Pennsylvanians' previous reluctance to vote for black candidates will not necessarily hurt Obama.

''Race is a factor in American life, ... but it doesn't preclude you from winning any vote,'' said Fattah, Pennsylvania's only black congressman. ''What you have to do is show you can identify with the issues and concerns of the people you are seeking support from.''

Like blacks, women also say party organizations could do more to promote their candidacies.

Barbara Hafer, a former auditor general and treasurer, is the only woman to run for governor on a major party ticket. As the Republican nominee, she was soundly defeated by incumbent Gov. Robert P. Casey in 1990.

Hafer had to launch her own political career; she wasn't recruited to be a candidate.

''You have to do it on your own, with your own family and friends,'' Hafer said. ''You cannot rely on party leadership.''

Serving in Pennsylvania's full-time legislature, where turnover in recent years has been below the national average, discourages some women with young families, given the time commitment it requires, said state Rep. Kathy Manderino, D-Philadelphia, who is single and has no children. She said women tend to capture more seats in states with high turnover and part-time legislatures.

Former U.S. Rep. Melissa Hart, a Republican, hears similar concerns when she talks to women about running.

''Invariably, I will get an answer _ 'When my babies are older,''' said Hart, who served three terms in Congress before her defeat in 2006.

Hart cut her political teeth as a campaign volunteer before running an upstart campaign for state Senate in 1990 _ upsetting a Democratic incumbent. A seminar for prospective GOP women candidates persuaded her to run. ''I would say that the old girls' network is growing,'' Hart said.

Ruth Rudy, a Democratic National Committee member who spent 14 years in the Legislature, said rural voters ''don't view women as being effective in positions of power as they do men.''

''When I first took my petition (for Legislature) around to get signed,'' said Rudy, who lives near State College in the center of Pennsylvania, ''there were people who said, 'I just don't think a woman is capable of handling the job.'''

But Pennsylvania didn't always trail other states in electing women. In 1922, two years after women got the vote, Pennsylvanians elected the first women to the Legislature. Eight won state House seats, making Pennsylvania a national leader, Manderino said.

Source: Associated Press