Over the past months, Republicans enjoyed enormous advantages. Opinion polls showed that voters are eager to reduce the federal debt, and they want to do it mostly but not entirely through spending cuts.

There was a Democratic president eager to move to the center. He floated certain ideas that would be normally unheard of from a Democrat. According to widespread reports, White House officials talked about raising the Medicare eligibility age, cutting Social Security by changing the inflation index, freezing domestic discretionary spending and offering to pre-empt the end of the Bush tax cuts in exchange for a broad tax-reform process.

The Democratic offers were slippery, and President Obama didn’t put them in writing. But John Boehner, the House speaker, thought they were serious. The liberal activists thought they were alarmingly serious. I can tell you from my reporting that White House officials took them seriously.

The combined effect would have been to reduce the size of government by $3 trillion over a decade. That’s a number roughly three times larger than the cost of the Obama health care law. It also would have brutally fractured the Democratic Party.