Sen. Barack Obama received endorsements Wednesday from a labor union and two Democratic superdelegates, as a poll showed he has cut Sen. Hillary Rodham Clinton's lead in Pennsylvania almost in half since mid-February as he strives to deny her a resounding victory in the state's presidential primary.

The Illinois senator peeled off an affiliate of the American Federation of State, County and Municipal Employees, which has endorsed Clinton. The Philadelphia-based local of the National Union of Hospital and Health Care Employees has about 16,000 members.

Its president, Henry Nicholas, announced the endorsement while introducing Obama at a meeting of the Pennsylvania AFL-CIO in Philadelphia.

Nicholas, who also is president of the 150,000-member national union and an AFSCME international vice president, said he took the step "because justice told me it was the right position to take."

Meanwhile Wednesday, Wyoming Gov. Dave Freudenthal and former Montana Sen. John Melcher both endorsed Obama. As superdelegates to the national convention, they are among the Democratic Party leaders who will decide the nomination, because although Obama leads Clinton in delegates neither one can win solely with pledged delegates awarded through primaries and caucuses. Obama handily won Wyoming's March 8 caucus; Montana holds a Democratic primary June 3.

Since last Friday, Obama has cut Clinton's lead among superdelegates by four; she has 250 to his 220.

Obama and Clinton campaigned Wednesday in Pennsylvania, whose presidential primary is April 22. A new poll showed Obama again eroding her lead here as he drew more support from men and young voters. The Clinton's 16-percentage-point lead in mid-February slid to 12 points in mid-March and now to nine points, according to the Quinnipiac University telephone poll, which ended March 31.

Clinton is well ahead of Obama among Pennsylvania's white voters, 59 percent to 34 percent, while Obama gets nearly three of four black votes. She is well ahead among women, while the two are even with men.

With both candidates wooing union members, displaced workers and anxious families, they quarreled again over which of them would oppose or modify trade deals such as the North America Free Trade Agreement. Some labor leaders blame NAFTA for sending U.S. jobs overseas, a claim that many economists dispute.

As many as 830,000 union voters are expected to have a strong say in how more than 4.1 million Democrats, a record registration for Pennsylvania, allocate the state's 158 delegates to the Democratic national convention.

Obama told the AFL-CIO gathering that he will oppose pacts that threaten U.S. jobs. His campaign scheduled a call with reporters Wednesday to underscore the role that Bill Clinton's presidency played in enacting NAFTA.

"What I refuse to accept is that we have to sign trade deals like the South Korea Agreement that are bad for American workers," Obama said.

He and Clinton have spent weeks arguing over which of them did or did not oppose NAFTA. The issue loomed large prior to March 4 primaries in Ohio and Texas that Clinton won. Speaking to the same unions a day earlier, Clinton said as first lady she had forcefully battled the agreement, which her husband labored hard to win.

"I did speak out and oppose NAFTA," she said. "I raised a big yellow flag and said, 'I don't think this will work.'"

The National Archives recently released most of Clinton's daily schedules as first lady. They showed her attending at least five meetings in 1993 aimed at helping win congressional approval of NAFTA.

The Obama campaign says the meetings show Clinton is misrepresenting her record on NAFTA. It got some help Wednesday from Teamsters president James P. Hoffa, who is backing Obama.

"No one who was around in the time of NAFTA remembers her doing that," Hoffa, speaking to The Associated Press by phone, said of Clinton's claim that she argued against NAFTA in 1993. "Let's face it, she's tied to NAFTA no matter what she says."

At an economic summit in Pittsburgh organized Wednesday by her presidential campaign, the New York senator said she would eliminate tax breaks for companies that move jobs to other countries and use the savings to persuade companies to keep jobs in the U.S.

Clinton's plan would offer new tax benefits for research and job development. It would also create "innovation and research clusters" across the country and provide $500 million annually in investments to encourage the creation of high-wage jobs in clean energy.

Clinton called it her "insourcing agenda."

"We hear so much about outsourcing," she said. "We all know what that is. It's when we lose jobs to other countries. I want to put an end to it. We're going to change the tax code, we're going to change the giveaways to the special interests."

Clinton also broadcast a new TV ad in Pennsylvania explicitly challenging Republican John McCain's economic credentials. Echoing an ad she targeted earlier at Obama on national security, it begins with images of sleeping children while a narrator says a phone is ringing in the White House at 3 a.m. but this time the crisis is economic. As the phone rings on and on, the sleeping children are replaced by adults grimly reviewing bills during daylight hours. The narrator faults McCain's response to rising home foreclosures and teetering markets and says he'd just let the phone keep ringing as the ad ends with an image of Clinton answering a phone.

AFSCME endorsed Clinton in October, and president Gerald McEntee is considered one of her biggest supporters. AFSCME does not prohibit its locals from endorsing separately. Only two, Illinois AFSCME Council 31 - in Obama's home state - and Oregon AFSCME Council 75, had endorsed Obama before Wednesday.

"It's unfortunate that the Hospital and Health Care Employees Union/District 1199C has decided to ignore AFSCME's endorsement of Hillary Clinton, especially since there is such a clear difference between the candidates on health care," McEntee said.

Obama responded Wednesday to Clinton's comparison of herself a day earlier to Rocky Balboa, the underdog boxer from Philadelphia in the 1976 film. She said "when it comes to finishing a fight, Rocky and I have a lot in common. I never quit. I never give up."

Obama told the union meeting: "We all love Rocky. But we've got to remember, Rocky was a movie."

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Associated Press Writers Alan Fram, Jesse Holland, Charles Babington and Mead Gruver contributed to this report. Beth Fouhy reported from Pittsburgh.