The Congressional Budget Office has estimated that for the Pentagon, that would mean a 10-percent cut in its $550 billion budget in 2013—a huge hit.

“Unless we act today, the dismantling of the greatest armed forces in history could begin tomorrow,” Rep. Howard P. McKeon, R-Calif., chairman of the House Armed Services Committee, wrote supercommittee leaders on Nov. 18 in a letter warning them of the consequences of the automatic defense reductions.

Senate Minority Leader Mitch McConnell, R-Ky., has said he wants to stick with the automatic cuts but would like to reshape them so they rely less heavily on defense.

Several lawmakers talked of the possibility of easing the impact of the automatic cuts on defense in interviews on Sunday news programs.

Rep. Jeb Hensarling, R-Texas, co-chairman of the supercommittee, said he hopes the current projected split of half defense, half domestic, for the automatic spending cuts will be changed in the event no deal emerges from his panel.

“But I am committed to ensuring that the American people get that deficit reduction that they were promised,” he said on Fox News Sunday. “But under the law, Congress will have 13 months to do that in a smarter, more prudent fashion.”

“Maybe sequestration is our only way we will get any kind of cuts,” Sen. Rand Paul, R-Ky., said on CNN’s “State of the Union.”

Rep. Jim McGovern, D-Mass., said on NBC’s “Meet the Press”: “If [Republicans are] going to try to protect defense, there’ll be pushback.”

On the domestic side, the law exempts Social Security, Medicaid, and many veterans’ benefits and low-income programs. It also limits Medicare to a 2 percent reduction.

Still, that leaves education, agriculture, and environmental programs exposed to cuts of around 8 percent in 2013, CBO says. For many Democrats, those are cuts worth fighting against, especially if Republicans try protecting defense programs.

The temptation to block the automatic cuts could grow even larger right after the 2012 elections, depending on the results.

The 2001 and 2003 tax cuts enacted under President George W. Bush are scheduled to expire in January 2013. Extending them is a top GOP priority, while Democrats want to let them expire for the highest-earning Americans.

If either party wins White House and congressional control, its members could be ready to reshape both the automatic spending cuts and the tax cuts to their liking.