Mr. Obama’s advisers are reportedly warning Democrats that allowing taxes to rise may cause a double-dip recession. The president can also warn them that it’ll be worse to settle this issue after Republicans take over the House in January.

If he fails, taxes will go up for every American on Jan. 1. If that happens, the new Congress would likely rectify the situation within days after being sworn in. The political damage to Mr. Obama would not be undone nearly as quickly. Failure to pass the tax compromise would make the president appear impotent. Confidence among Democrats would collapse. And there would be more challenges to Mr. Obama’s leadership from within his own party, perhaps even in the 2012 primaries.

Most importantly, failure would imperil $400 billion in tax cuts that would be a more effective economic boost than Mr. Obama’s justifiably ridiculed stimulus. Without much healthier economic growth and far more robust job creation, Mr. Obama has little chance of wooing back the independents who elected him in 2008 yet abandoned Democrats in 2010.