Behind the open brawling over how to rebuild the nation's health-care system, another struggle is beginning to erupt that may become the toughest test of all for the historic drive to cover millions of people without health insurance and improve medical care for everyone else -- who should pay the eye-popping bill. President Barack Obama and his congressional allies -- who are also struggling to hold down the national debt after years of deficit spending and a rush of new outlays to combat the recession -- have pledged to come up with more than $1 trillion over the next decade to offset the costs of what would be the biggest health overhaul in generations. But the prospect of new taxes, new fees for businesses and cutbacks in other government spending has set off a furious behind-the-scenes struggle. Faced with a proposal to increase the tax on liquor and soft drinks, for instance, the liquor lobby sent San Francisco brewer Anchor Steam to talk to House Speaker Nancy Pelosi, D-Calif. The brewery found a wholesome ally in milk manufacturers who object to the proposal because it would raise the cost of chocolate milk. And when congressional Democrats started warming up to the idea of curbing the once-sacrosanct tax break for employer-provided health benefits, the labor movement went on the air to attack one of the idea's leading champions, Oregon Sen. Ron Wyden, among the Senate's most liberal Democrats. 'I suspect what will emerge as the toughest issue for lawmakers is not the ideological debate about the role of government, because there is some consensus there about the need for a centrist approach. Rather, it will be how to pay for the plan,' said Drew Altman, president of the nonprofit Kaiser Family Foundation. To date, much of the maneuvering has happened behind closed doors, as interest groups remain reluctant to appear too intransigent and risk getting shut out of negotiations that are expected to drag through the summer and fall as lawmakers work through the massive legislation. But the jockeying is expected to ratchet up in coming weeks. And it's already worrying Democrats on Capitol Hill, where there is still little consensus about how to come up with hundreds of billions of dollars that are needed. Obama, who at a White House meeting Wednesday urged a bipartisan group of senior lawmakers to press ahead with health-care legislation, is stepping up his efforts to build momentum behind the legislative push. He travels to Wisconsin Thursday for a town hall meeting focusing on health care. Underscoring the difficulties, senior administration officials said last week that the $2 trillion in savings promised by a health-care industry group working with the White House will not pay for an expansion in coverage. So far, neither the president and nor senior Democrats have provided more than scant details about how they plan to raise the money. A recent poll by the Kaiser Family Foundation found solid majorities of Americans favor some proposals for funding a health overhaul, such as higher taxes for families making more than $250,000 and additional taxes on cigarettes and alcohol. Other ideas, such as taxing sodas and unhealthy snack foods are considerably less popular, as is an across-the-board income tax hike. And even general talk of specifics has stirred interest groups to action. Obama sparked an immediate backlash when he laid out plans in his budget to raise nearly $300 billion over the next decade by cutting payments to insurers that contract to provide Medicare to seniors under the so-called Medicare Advantage program. The insurance industry mobilized thousands of senior citizens by organizing 'Medicare Advantage Community Meetings' across the country. The AARP blanketed offices on Capitol Hill with letters warning lawmakers not to do anything that would risk cutting benefits to seniors. Others rebelled at a second Obama proposal to come up with an additional $300 billion by reducing the deductions that high-income taxpayers could take on charitable contributions, home mortgage interest and state and local taxes. Charitable organizations, who claimed the change would reduce the incentive for people to give to nonprofits during a recession, were so successful getting their message across on Capitol Hill that home builders and realtors did not even bother mounting a lobbying campaign. Congressional ideas have fared little better, with lobbyists fanning out on Capitol Hill to challenge proposals to levy fees on businesses that don't provide health insurance and to raise taxes on liquor and sugary drinks, So high are the stakes that many interest groups are now competing to convince lawmakers that they can't afford to get saddled with a health-care tab. 