At the same time, both sides have worked to tilt the bargaining table to their advantage. As part of that effort, Obama travels to Pennsylvania on Friday to campaign for his tax proposal.Boehner, who will begin a second term as House speaker early next month, has appealed to his rank and file to remain united. At a closed-door meeting this week, he displayed polling data that showed the public would rather see loopholes closed than rates raised as a means of raising revenue for the government. At the same time, there are tremors within the GOP ranks, with a small number of Republicans saying they are willing to let tax rates rise at upper incomes in view of the election returns, and others predicting legislation to that effect would pass the House if put to a vote. ___ Associated Press writers Jim Kuhnhenn, Julie Pace, Alan Fram, Stephen Ohlemacher and Andrew Taylor contributed to this story.