Missing the Dec. 31 deadline would change the political dynamics and make it easier for many lawmakers to agree to a second-chance compromise in the new year.
That's especially true for scores of House Republicans who have vowed never to vote to raise tax rates.
Virtually every American's taxes will automatically go up if no accord is reached by Dec. 31. Republicans in the new year could then vote to cut taxes for about 98 per cent of Americans.
President Barack Obama could achieve his goal of raising taxes on the richest 2 per cent without having to make anyone vote to do it.