G.O.P. Split Over Bid to Revise Budget Deal WASHINGTON - The House is bracing for a rancorous showdown over a 2013 budget plan that has already divided Republicans because of a push by conservatives to cut spending below the level both parties agreed to in last year's deal to raise the federal deficit. Trying to demonstrate anew their push to reduce the size of the government, conservative House Republicans want to cap spending on programs under Congress's discretion well below the $1.047 trillion cap set by the budget deal last summer. But House Appropriations Committee leaders and Republican moderates, facing tough re-election campaigns, want to stick to the agreement struck with President Obama seven months ago. We voted for it. That's the number we should use," said Representative Charles Bass, Republican of New Hampshire. The budget blueprint for the coming fiscal year - to be unveiled next week - will also reignite the fight over Medicare, an election-year prospect that has both parties digging in. Whatever the House produces, Senator Harry Reid of Nevada, the majority leader, has already said he has no intention of bringing a budget to a vote in the Senate - meaning the House debate will be essentially symbolic. But the symbolism could define the battle for control of the House in 2013 between Republicans - who say they are willing to make the difficult choices to overhaul Medicare, limit the size of government and control the deficit - and Democrats running as a party that will preserve Medicare and make the rich shoulder more of the economic burden. "An argument for a sounder, more sensible future for Medicare is one that we can very comfortably make," said Representative Nan Hayworth of New York, a freshman Republican on the Democrats" target list. Before they can get to that debate, Republicans must decide among themselves whether and how far to break the agreement on spending levels reached in July during the last budget fight, the one over raising the statutory limit for federal borrowing. Last week, House Budget Committee Republicans met privately with Representative Eric Cantor of Virginia, the majority leader, to try to set a spending limit for the 2013 fiscal year that almost certainly would be below the cap set last year. That brought indignant protests from Democrats and predictions of another spending stalemate, this time just before the November election. The Senate will stick with the $1.047 trillion figure, meaning House and Senate spending bills will start out tens of billions of dollars apart. Senator Kent Conrad, a North Dakota Democrat and chairman of the Senate Budget Committee, said the budget deal spending levels should be more sacrosanct than a conventional nonbinding budget agreement since the debt limit figure is enshrined in law. Democrats say that if the House and Senate stick to that number, Congress could devote much of its energy to working on a long-term deficit reduction plan that would be ready for a vote shortly after the November election. Instead, the Capitol could again be tied in knots over differing levels of spending in a dozen routine spending bills. "I do not understand their fascination with government shutdowns and looking dysfunctional," said Senator Patty Murray, Democrat of Washington, a senior member of the Appropriations Committee. Beyond that number loomed another fight over Medicare, the health care program for the elderly. House Republicans say their new budget will step back from last year's plan, which would have replaced the guaranteed benefits of Medicare with a fixed government allowance that the elderly would receive to purchase private health care. Instead, the elderly would be offered an allowance that could be used to buy a private plan or the existing government coverage, a proposal embraced by the House Budget Committee chairman, Paul D. Ryan, Republican of Wisconsin, and Senator Ron Wyden, Democrat of Oregon. House Republicans are using Mr. Wyden's name as a political shield. In an interview, Ms. Hayworth used the term Wyden-Ryan three times. But some Republicans are returning to the Medicare fight with trepidation this election year. Yet despite the unease, House Republicans say they are willing to produce a budget, even if the Senate does not. "The point is to lay that marker out there and say this is the preferred path forward," said Representative Steven C. LaTourette, a veteran Republican from Ohio, "and then like so many things, the Senate and the administration are going to have to come up with some way to deal with it. I'm perfectly comfortable with that. What's not worth it is to come up with some goofy, pie-in-the-sky entitlement reform that's never going to happen, and that's going to expose our members to criticism. Democrats are not waiting. The Democratic Congressional Campaign Committee has produced a mock movie poster proclaiming, "Just when you thought Medicare was safe, they're back." Representative Steve Israel, the committee's chairman, predicted that the budget fight could define the 2012 election campaign for his party, especially if, as expected, the budget eschews any tax increases. "Instead of asking seniors to be the first to experiment," Mr. Israel said, "why not ask millionaires to do a little more? That's the dividing line. The Republican presidential front-runner, Mitt Romney, provoked the first skirmish of the fight on Monday when he tried to turn the political tables and accuse Mr. Obama of "ending Medicare as we know it." The Romney campaign pointed to Medicare cuts in the 2010 health care law and the law's newly created independent board empowered to press for Medicare cost savings. Democrats fired back with Mr. Romney's embrace of the Ryan approach to Medicare changes.