The idea that you’d shut down the federal government — or, perhaps, default on the national debt — to kill Obamacare is not just a “bad idea,” as President Barack Obama described it on Aug. 9. It’s utterly irresponsible, pure madness — and suicidal for the Republican Party to boot.

With economic growth running under 2 percent a year, a government shutdown or debt default would stifle the recovery and spike unemployment. And the consequences surely would be blamed on Republicans, much as the 1995-96 government shutdown that helped re-elect Bill Clinton.

Already, according to a July NBC-Wall Street Journal poll, 56 percent of voters said they think Republicans in Congress are “too inflexible in dealing with President Obama,” while only 18 percent  think they are “too quick to give in.”

It’s true that Obamacare is unpopular, but it’s not so unpopular that risking economic disaster to secure its repeal would be a political winner. In the WSJ-NBC poll, 47 percent of voters said the law was a “bad idea” to 34 percent who think it’s a good idea. But 51 percent said Republicans should stop trying to block the law and move onto other priorities, while 45 percent favored their doing everything possible to block it.

There’s plenty of reason to think that what Obama termed the “glitches” in implementation of the Affordable Care Act will prove to be serious — and will benefit Republicans politically in 2014 and even 2016. Insurance premiums are already up some 40 percent for individual buyers in some markets. Health care costs have to rise as millions of new customers start buying into an already-costly market. There will be regional doctor shortages and confusion in the states as they try to open insurance exchanges and expand Medicaid.

The responsible thing for Republicans to have done over the years since Obamacare was passed — and to be doing now — is to offer proposals to improve it or replace it with something better. They’d have more standing to criticize and would have an alternative to put forward if the public really began demanding repeal.

Actually, in 2009, Sens. Tom Coburn of Oklahoma and Richard M. Burr of North Carolina, and Reps. Paul D. Ryan of Wisconsin and Devin Nunes of California did introduce the Patients’ Choice Act. It was a rather radical, market-based proposal that would have replaced the employer-based health insurance system with tax credits for individuals, who’d then buy their own insurance through state-based exchanges.

The Coburn-Ryan bill had flaws — it offered only a $5,700 annual rebate for families when the average employer is currently paying a premium of nearly $16,000. If the bill had been considered and refined, however, the GOP would have something it could offer to the public, which still thinks Democrats have better ideas on health care than the GOP.

Instead, Republicans have just railed against Obamacare, passed meaningless resolutions to dismantle it and, as Obama said, made its repeal an “ideological fixation.”

Now, ideologues led by Heritage Foundation chief Jim DeMint and Sens. Mike Lee of Utah, Ted Cruz of Texas and Marco Rubio of Florida want to stop funding the government unless Obamacare is repealed.

The same mentality led House Republicans to temporarily block President George W. Bush’s 2008 bank rescue package, to nearly default on the national debt in 2011 and to advance the likes of Sharron Angle, Christine O’Donnell and Richard Mourdock for the U.S. Senate. It’s madness.