Senior Democrats in the House of Representatives said they would insist President Barack Obama provide hard evidence that proposed free trade deals will boost median U.S. incomes, laying out tough terms to support his trade agenda. The demands, hours before Obama's address to a House Democratic retreat, are part of a renewed focus by the party on middle-class economic issues. Republicans have made free trade a top priority and have called on Obama to bring Democrats into line. Obama last week proposed shifting tax breaks from the wealthy to the middle class. He also asked Congress to give him "fast-track" authority to negotiate trade agreements, something many Democrats oppose, fearing American workers would lose more ground. "Show me a trade deal that not only increases GDP (gross domestic product), but increases the average worker's monthly paycheck and I'll be for it," Representative Steve Israel told reporters. "That's the message. We're open to a trade deal, but it's got to increase median household income and not just GDP. And if the administration can get us there, it will pass with Democratic votes.” Virginia's Gerry Connolly, a leader of the pro-trade New Democrats, sees no more than 50 Democratic votes and other pro-trade Democrats see 25-40 votes. Representative Chris Van Hollen, the top Democrat on the House Budget Committee, said each trade deal will need to demonstrate stronger paychecks and wages for American workers, but it will be difficult to evaluate the 12-nation Trans-Pacific Partnership (TPP) agreement now being negotiated. Israel, who headed House Democratic campaign efforts during November elections that ceded Senate control and more House seats to Republicans, now has a senior role shaping the Democratic Party's message. He said many middle class workers felt cheated by manufacturing job losses after the 1994 North American Free Trade Agreement, and worry the U.S. economy could slip back into recession. Illustrating the resistance within the party, Senate Democratic leader Harry Reid and three colleagues are circulating an online petition against fast-track. Obama, in a question-and-answer session with the lawmakers on Thursday, acknowledged that previous U.S. trade deals had not been perfect, according to a source in the room. Obama also pledged to work with House Democratic leader Nancy Pelosi to ensure lawmakers had more information about the substance of the deals as they come together. Some Democrats, including the party's senior member on the House committee responsible for trade, Sander Levin, say they will only support the TPP if it tackles currency manipulation and enforceable labor rights. Others such as Senator Michael Bennet are looking for a good deal for farmers, while Senator Robert Menendez said that 12 years of protection for biologic drugs is a "critical issue" for him. (Reuters)