Republicans have no leverage in the upcoming debt-ceiling debate, former Rep. Denny Rehberg warned this week.

The Montana Republican, retired from Congress after losing a Senate bid last November, said the GOP leaders who are threatening to allow a government default to win more spending cuts would suffer a public backlash for years to come.

"If you don’t raise the debt ceiling, the financial markets melt down, then who’s mad at you? Well, every Republican out there who’s in small business, who needs credit, who needs a sound banking system starts calling Republicans saying, 'Cave, cave, you’ve gotta give in, you’ve gotta cut a deal,'” Rehberg said in a Thursday interview with the Voices of Montana radio show.

"If they become obstructionists, what power do they have? Well, shutting government down? No, because if we do that we lose our support with the public.”

With the Treasury Department warning that the country will default on its obligations unless Congress raises the debt limit in the next two months, Washington is bracing for the next partisan battle over government spending.

President Obama and the Democrats want a clean debt-ceiling increase, with a broader talk about taxes, entitlements and spending to follow.

"One thing I will not compromise over is whether or not Congress should pay the tab for a bill they’ve already racked up," Obama said Saturday in his weekly radio address.

Republicans, however, want to marry spending cuts to the debt-ceiling hike, viewing that legislation as their best chance to hold the Democrats' feet to the fire and force significant reductions.

Sen. John CornynJohn CornynTrump gets chance to remake the courts Lawmakers eye early exit from Washington Victims of Nazi Art theft need Congress to HEAR MORE (Texas), the second-ranking Senate Republican, summed up that strategy on Friday, vowing to shutter the government if the Democrats don't include major cuts as part of the debt-ceiling deal.

“It may be necessary to partially shut down the government in order to secure the long-term fiscal well being of our country, rather than plod along the path of Greece, Italy and Spain," Cornyn wrote in a Houston Chronicle op-ed. "President Obama needs to take note of this reality and put forward a plan to avoid it immediately."

Rehberg is warning, however, that such a strategy backfired on former House Speaker Newt Gingrich in the mid-90s, and would do so again on Speaker John BoehnerJohn BoehnerLobbying World 'Ready for Michelle' PACs urge 2020 run News Flash: Trump was never going to lock Clinton up MORE (R-Ohio) if they go that route this year.

"The only thing the Republican Congress, the House, can do, is things like shut down [the] government. Well, [Newt] Gingrich tried that, and the public reacted – Republicans as well as Democrats – came out and said, 'Whoa, whoa, whoa, wait a minute.' We started hearing from realtors, builders, bankers, contractors and ranchers who call themselves conservatives but [revolt] when they don't get their BLM lease … All of a sudden your coalition of support evaporates," Rehberg said Thursday.

"I understand the frustration Republicans and the Tea Party and such, but I’m just telling you, this is from my heart, I want to be as honest as I possibly can, that you’ve got a Democrat president, a Democrat-controlled Senate and they outnumber BoehnerJohn BoehnerLobbying World 'Ready for Michelle' PACs urge 2020 run News Flash: Trump was never going to lock Clinton up MORE and the Republicans two to one and nothing’s going to change that for the next two years."