Senator Hillary Clinton won the Democratic primary in Pennsylvania Tuesday by 10 percentage points, extending the contest for the presidential nomination, although Senator Barack Obama retained a significant lead in the national delegate count.

With more than 90 percent of the vote tabulated in Pennsylvania, Clinton had a substantial lead, 55 percent to 45 percent, in the popular vote, and a narrower lead in pledged delegates selected on the basis of the vote totals in the state’s 19 congressional districts.

The demographic and geographic split among Democratic primary voters was substantial. Obama won 90 percent of the votes cast by African-Americans, while Clinton won 67 percent of those cast by white voters. Clinton won sizeable majorities among voters with incomes under $50,000 a year and among voters in small towns and rural areas.

Obama took a large majority of the votes of those under 30, while Clinton took even greater margins among the elderly, who constituted a much larger share of the vote in Pennsylvania than in most other primary states. Young voters were only 12 percent of those participating, while 22 percent were over 65.

Obama carried only seven of the state’s 67 counties, including Philadelphia and two of its suburban counties, as well as Lancaster, Dauphin (Harrisburg) and two counties around State College, where Penn State University is located. Obama had 63 percent of the vote in Philadelphia, the most populous county, but Clinton carried Allegheny County, the second largest, which includes Pittsburgh, with 54 percent.

Clinton won every county in the economically devastated industrial areas of western and northeastern Pennsylvania, with margins of over 70 percent in Luzerne County (Scranton) and in the four counties in the state’s southwest corner—Greene, Washington, Fayette and Union, once the center of coal mining in the region.

Exit polls found Obama winning among voters who said the war in Iraq was the most important issue, about one-fourth of the total, while Clinton won majorities among those who said the economy (more than 50 percent) and health care (14 percent) were the most important issues.

Turnout surged in Pennsylvania, as it has in most primary states this year. More than two million voted, double the number in the 2004 primary and approaching the total vote for Democratic presidential candidate John Kerry in the general election.

Clinton’s 200,000-vote margin in Pennsylvania cuts into Obama’s national lead in the popular vote in all Democratic primaries of about 700,000. The Clinton campaign argues that vote totals in Florida and Michigan would make the race a virtual tie in terms of the popular vote, with about 13,500,000 votes for each candidate. Both states were stripped of their delegates for moving up the dates of their primaries, and Obama’s name was not even on the ballot in Michigan.

In terms of delegate votes, the Pennsylvania result had a relatively small impact. As of late Tuesday night, Clinton had a lead of 56-50 among pledged delegates whose election was declared by that time. The allotment of the remaining 52 pledged delegates in the state will be determined by sometime Wednesday.

This net gain of six only slightly reduces Obama’s estimated lead of 141 delegates, with an Associated Press tabulation showing 1,714 delegates for Obama, counting both pledged delegates and so-called “super delegates,” and 1,573 for Clinton.

The final week of the campaign featured increasingly sharp media attacks on Obama, particularly in last Wednesday’s televised debate, and a huge advertising blitz by the Obama campaign, which spent a record $9 million on television commercials alone.

The Clinton campaign also spent substantial amounts, and her final television commercial emphasized the increasingly right-wing character of her campaign, featuring images of Osama bin Laden and Pearl Harbor to underscore the message that she would be a “commander-in-chief” ready and willing to use military force.

In an extraordinary declaration on the day of the primary, Clinton warned that if she were president the United States would “totally obliterate” Iran should the Iranian government launch an attack against Israel. “I want the Iranians to know that if I’m the president, we will attack Iran,” she told the ABC television program “Good Morning America.”

“In the next 10 years, during which they might foolishly consider launching an attack on Israel, we would be able to totally obliterate them,” she said. “That’s a terrible thing to say, but those people who run Iran need to understand that because that perhaps will deter them from doing something that would be reckless, foolish and tragic.”

This was an escalation of militaristic threats even over those she made in the April 16 debate, when she threatened “massive retaliation” against Iran in the event of an attack on Israel or other US-allied regimes in the Middle East.

Obama declined to match Clinton’s rhetoric, saying, “I’m not interested in saber-rattling.” But he hastened to add that he would respond “forcefully and swiftly” to an Iranian attack.

The Clinton campaign in Pennsylvania sought to combine anti-terrorist fear-mongering with appeals to the economic grievances of working class voters. Campaign spokesmen have increasingly voiced arguments about “electability,” echoing the McCarthy-style smear campaign against Obama by sections of the media and the ultra-right, particularly over Obama’s former pastor, Jeremiah Wright.

It was also revealed that Clinton had attacked the liberal Democratic Moveon.org group—originally formed to defend Bill Clinton against impeachment—for its support to the Obama campaign. According to a tape recording of remarks in February, leaked to the press last week, Clinton said that antiwar activists “flood into these caucuses and dominate them and really intimidate people who actually show up to support me.”

Clinton also collected the endorsement of the Pittsburgh Tribune-Review, owned by billionaire Republican Richard Mellon Scaife, the main financier of the right-wing campaign against her husband that ultimately produced his impeachment. Every other major newspaper in Pennsylvania endorsed Obama—an indication of his increasing support among business interests.

The Obama campaign has sought to stave off the renewed challenge from Clinton by consolidating its support in the Democratic Party establishment, and particularly from the most conservative elements. In the past two weeks, Obama has received endorsements from former Democratic senators Sam Nunn of Georgia and David Boren of Oklahoma, from former Indiana congressman Lee Hamilton, a member of both the 9/11 commission and the Iraq Study Group, and a slew of Democratic congressmen and state legislators, mainly from southern and border states.

The Obama campaign has also built up a huge financial advantage over Clinton, with an estimated $42 million war chest to fund campaigning through June 3, compared to less than $10 million for Clinton, whose debts actually exceed her cash on hand.