None of the outcomes is good for the Democrats. The Republicans struck a deal with the President to prevent significant tax increases from crippling the economy. It's hard to understand why they could be expected to re-open negotiations either to placate the left wing of a party that ran roughshod over them when it had the chance, or to save the bacon of a President who has -- up until fate forced his hand -- offered them neither respect nor attention.
In the end, this is a Democratic issue. Either the President, nominally the head of the Democrat Party, is empowered to negotiate on behalf of Democrats, or he is irrelevant. If it's the former, there will be no economy-crippling tax increases. If it's the latter, he, the Democrats, and American taxpayers are in for a lot of pain.