SUMTER, S.C. >> Sen. Lindsey Graham rode last week like Paul Revere from South Carolina’s wooded upstate to its gracious Lowcountry to its sweltering midsection, offering a bureaucratic rallying cry for his military-heavy state — the defense cuts are coming.

On Jan. 2, national security is set to receive a heavy blow if Congress fails to intervene. That is when a 10-year, $600 billion, across-the-board spending cut is to hit the Pentagon, equal to roughly 8 percent of its current budget.

Graham’s colleagues in the Senate have been strangely quiet about the impending cuts, set in motion last summer when the Budget Control Act ended an impasse over raising the nation’s borrowing limit with a deal designed to hurt both parties if they did not strike an agreement later on. A special select committee was assigned to come up with at least $1.2 trillion in deficit reduction over 10 years. If it failed, the cuts would come automatically, half to national security, half to domestic programs.

It failed, and the reckoning is approaching.

“Our ability to modernize will be basically gutted,” Graham told National Guard officers in Greenville. The Marine Corps will have to choose between its massive training camps in San Diego or Parris Island, he told community leaders in Beaufort, a stone’s throw from Parris Island.

The C-17 fleet at Joint Base Charleston would be “devastated,” he warned city leaders at the Charleston Chamber of Commerce. The cuts to the soldiers and airmen at Shaw Air Force Base would leave behind a “hollow force,” he intoned in a windowless room at the Quality Inn in Sumter.

In fact, no one knows what “sequestration,” the term for the automatic cuts, will look like, not lawmakers, not the military. But Republicans who helped create it as a bludgeon to force a bipartisan budget accord are now desperate to undo it. Indeed, some of the loudest advocates for blocking the cuts — like Rep. Howard P. McKeon of California, chairman of the House Armed Services Committee, and Sen. John McCain of Arizona, the ranking Republican on the Senate Armed Services Committee — voted to create them; 28 Senate Republicans and 174 House Republicans voted for the Budget Control Act, overwhelming the opposition.

But the threat they created may be doing its job. Graham is openly talking about revenue increases to offset the costs. Even South Carolina’s ardently conservative House members, Mick Mulvaney, Joe Wilson and Jeff Duncan, said last week that they were ready to talk.

“I’m personally offended that they’re playing a high-stakes game of chicken with our national defense,” fumed Weston Newton, chairman of the Beaufort County Council, after hearing Graham’s dire warnings.

Eugene R. Baten, chairman of the Sumter County Council, told the senator of the 1-cent sales tax increase that helped finance a land purchase to protect Shaw from encroaching development. “We have sacrificed as a community,” he said. “But we can’t do it alone. I’m not saying it’s the Democrats’ fault. I’m not saying it’s the Republicans’ fault. It’s both of y’all’s fault.”

On its face, the automatic cuts do not sound that bad. If they are put into effect, military spending would decline to its 2007 level, said Todd Harrison, a senior fellow for defense budget studies at the Center for Strategic and Budgetary Assessments. But really it is worse than that. The law exempts war costs and allows the administration to wall off personnel levels and military pay, about a third of the Pentagon budget. That means everything else — operations and maintenance, research and development, procurement, fuel, military construction — would face immediate cuts as deep as 13 percent, Harrison said.

And under the law, the Defense Department could not do the kind of planning that would rationalize the cuts. Graham warned the citizens of Beaufort that the Marines would have to shut either their Parris Island or San Diego training camps, and would face the same choice between their airfields at Beaufort or Cherry Point, N.C. In fact, under the law, all bases face the same cuts because Congress has prohibited base closings.

The dire warnings are not coming from Graham alone. They are coming at least as loudly from Leon E. Panetta, the secretary of defense. The administration, with the assent of some Republicans like Graham, has agreed that the Pentagon will contribute around $450 billion in deficit reduction over the next decade. Tack on $600 billion more and the impact will be debilitating, Pentagon officials say.

But those warnings have not gotten Panetta very far. In May, the House did vote to shift the first year of automatic defense cuts to domestic spending, but the legislation did not get a single Democratic vote and will go nowhere in the Senate. Even some Republicans recoiled at foisting Pentagon cuts onto programs like food stamps and school lunch programs.

“I voted my conscience, and I voted my district,” said Rep. Michael G. Fitzpatrick, R-Pa., who voted against the shift to heavier domestic cuts. “Reductions like this need to be equitably shared across the agencies.”

Sen. Harry Reid of Nevada, the majority leader, has given no indication that he will undo the cuts without a broader deficit reduction deal that would include revenue increases — and no such negotiations are under way.

Rep. Chris Van Hollen of Maryland, the ranking Democrat on the House Budget Committee, said Republicans were given the choice during the debt ceiling negotiations between automatic defense cuts or automatic tax increases in the event that the “supercommittee” failed to reach a deficit deal. They chose the defense cuts.

“The consistent pattern here is they have chosen to defend special interest tax breaks over defense spending,” Van Hollen said. “They made that choice.”

Graham’s intention is to separate defense from the larger deficit issue by aiming his arguments high and low. The high argument is about American greatness.

“The debate on the debt is an opportunity to send the world a signal that we are going to remain the strongest military force in the world,” he said. “We’re saying, ‘We’re going to keep it, and we’re going to make it the No. 1 priority of a broke nation.”’

To that end, his arguments grow increasingly complex, involving a near-term confrontation with Syria and what he is sure will be a military strike on Iran late this summer, “an air and sea campaign from hell,” he tells an audience in Sumter. A large screen at the 3rd Army command center in nearby Shaw Air Force Base seemed to back him up on that. It broadcast a multicolored map of Iran with its air defenses demarcated in loud, red circles.

Then there is the low road: fear.

“The soft underbelly that I’m trying to exploit is, ‘What does this mean to your state?”’ he said.

The audience for that appeal could be forgiven for greeting it with a yawn. So far, at least, Congress is acting as if the constraints it imposed on itself in August will simply be ignored. The House in May approved an annual defense policy bill that authorized Pentagon spending $8 billion higher than spending caps approved in the Budget Control Act — without the automatic spending caps. The Senate Armed Services Committee stuck largely to those caps but included nothing to prepare for sequestration beyond ordering up a study of its potential impacts.

Military leaders in South Carolina came to the microphones of Graham’s events, speaking of “insidious” impacts and “devastating blows.” But pressed privately, Maj. Gen Robert E. Livingston Jr., South Carolina’s elected National Guard adjutant general, conceded:, “We don’t know what sequestration looks like. There hasn’t been a whole lot of planning.”

For now, Democrats and Republicans are waiting for the other side to blink. And the pressure may be working. Graham said the sentiment for raising revenues by closing tax loopholes or imposing higher fees on items like federal oil leases is expanding in his party.

Asked about the “no new taxes” pledge almost all Republicans have signed, he shrugged: “I’ve crossed the Rubicon on that.”