LYNDHURST, Ohio -- New York Sen. Hillary Rodham Clinton yesterday sharpened her populist message in a state that is crucial for her Democratic presidential nomination hopes, while her rival, Illinois Sen. Barack Obama, picked up the endorsement of a key union and a prominent former Clinton supporter.

"We're going to be returning money to the hardworking people in Ohio," Mrs. Clinton told a crowd that packed a Lyndhurst high school gymnasium. "We are going to take on the special interests who stand in the way of your having more disposable income, because they've been able to take advantage of you for the past seven years."

The former first lady crossed Ohio, starting in Cincinnati and ending the day in this Cleveland suburb. Her campaign has placed heavy emphasis on the state, which votes March 4, as a "firewall" against Mr. Obama's momentum following her defeat in eight straight primary contests across the nation.

The Obama campaign yesterday received a string of good news. The New York Times reported that Rep. John Lewis, D-Ga., a veteran civil rights leader and a Democratic convention superdelegate, said he planned to cast his vote for Mr. Obama. He had previously announced support for Mrs. Clinton, but said he has been impressed by the Illinois senator's campaign performance.

"In recent days, there is a sense of movement and a sense of spirit," The Times quoted Mr. Lewis as saying. "Something is happening in America, and people are prepared and ready to make that great leap."

A Lewis spokeswoman yesterday suggested the Times report was "inaccurate," but the Atlanta Journal-Constitution last night quoted Rep. Jim Clyburn, D-S.C., a close friend of Lewis, as saying, "John is wrestling with this."

Mr. Obama also won the endorsement of the 1.9 million-member Service Employees International Union, a day after he received the support of the United Food and Commercial Workers, a union with 69,000 members in Ohio.

But Mrs. Clinton still has a strong lead in the state and in neighboring Pennsylvania, according to a poll released this week.

The two campaigns continued a war of words over free trade, a highly contentious issue in Ohio, where trade pacts such as the North American Free Trade Agreement are often blamed for losses of manufacturing jobs.

Mrs. Clinton's campaign slammed the Obama camp for sending out a mailing that it said misrepresented her position on NAFTA, which took effect when her husband, Bill Clinton, was president. "Hillary Clinton believed NAFTA was 'a boon' to the economy," the Obama mailing says, citing a chart in Newsday in 2006 during her Senate re-election campaign in New York.

The newspaper ran a clarification on its Web site yesterday, acknowledging that the chart did not directly quote Mrs. Clinton. "Obama's use of the citation in this way does strike us as misleading," the newspaper said. "The quote marks make it look like Hillary said 'boon,' not us. It's an example of the kind of slim reeds campaigns use to try to win an office."

Mrs. Clinton has said she would review all trade agreements if she becomes president, and she has called for a moratorium on future pacts until protections for American workers can be put in place.

During a conference call with reporters, Rick Sloan, communications director for the International Association of Machinists, compared Mr. Obama's mailing to all-star pitcher Roger Clemens' appearance at a congressional hearing this week on steroid use in baseball. "I think if you can believe Roger Clemens, you can believe Barack Obama," said Mr. Sloan, whose union is backing Mrs. Clinton.

He accused Mr. Obama of not fighting to keep open a Maytag plant in Galesburg, Ill., in 2004. "There's shadowboxing, and then there's real fighting," he said.

Meanwhile, Mr. Obama continued to criticize Mrs. Clinton on trade and other economic issues.

"Her supporting NAFTA didn't give jobs to the American people," he said in Milwaukee. "Her supporting a bankruptcy bill made it harder for people to get out of debt, and that didn't help them with the bills that were stacking up on their desks."

His campaign is running radio advertisements in Ohio that tout his time as a community organizer on Chicago's South Side, helping unemployed steel workers.

Mr. Obama's wife, Michelle, campaigned in Cincinnati yesterday, while the candidate himself was in Wisconsin, which holds its primary Tuesday. He is favored to win there, but Mrs. Clinton plans to campaign in the state over the weekend. Her campaign hopes to stave off another lopsided Obama victory, or perhaps even manage an upset win.

More than 1,000 people waited outside in the cold for several hours to hear Mrs. Clinton at Lyndhurst's Brush High School.

"She talks about a plan. Her plan has substance. Obama is just about rhetoric," said Gwen Korb, 63, a self-employed artist from the Cleveland suburbs. "Barack Obama always talks about change. In my opinion, when Bush became president, that was a huge change. Change isn't always good. It depends on the person."

It was an issue Mrs. Clinton echoed in her stump speech:

"There's a big difference between speeches and solutions, between talk and actions," she said, her voice hoarse from the strain of the long campaign. "I have the highest regard for my opponent. I just believe that if you're hiring a president, I would be the one you hire for this job."

Not everyone was convinced that Mrs. Clinton was that person, especially some high school students who came out to hear the former first lady. "I see more people leaning toward Obama," said Vikram Ramanujam, a senior. "I think he speaks to a younger population."

Mr. Obama received some more Ohio support this week. The Democratic National Committee allowed its former chairman, David Wilhelm, to qualify as an unpledged superdelegate in the Buckeye State.

Mr. Wilhelm, who managed Bill Clinton's 1992 presidential campaign and is now an Obama supporter, moved from Illinois to Ohio in 2005, according to The Plain Dealer newspaper.

Ohio now has 21 superdelegates in addition to 141 delegates that will be apportioned based on results of its March 4 primary. Gov. Ted Strickland and U.S. Rep. Stephanie Tubbs Jones are two of Mrs. Clinton's supporters among the superdelegates.