WASHINGTON  The collapse of a government-wide spending package in the final days of this Congressional session sets up a politically charged fiscal showdown early next year, testing the determination of Republicans about to take over the House with promises to slash an array of domestic programs.

As Congress struggled to assemble a stopgap measure to finance the government at least into the first months of 2011, House and Senate Republicans on Friday hailed their ability to derail a $1.2 trillion spending measure put forward by Senate Democrats, and promised to use their new Congressional muscle to respond to public demands to shrink government.

“Beginning in January, the House is going to become the outpost in Washington for the American people and their desire for a smaller, less costly and more accountable government,” said Representative John A. Boehner of Ohio, the incoming House speaker.

“I will tell you,” he added, “we are going to cut spending.”

With the lame-duck session entering its final days, there was an air of partisan chaos on Capitol Hill as both parties scored important legislative victories and events changed on an almost hour-to-hour basis as the end of Democratic control of the House approached.