McClintock has nicely trapped the Dems. The Car Tax increase was the one significant "revenue enhancement" that arguably did not require a 2/3 majority vote, and which the Democrats could therefore pass without the support of any Republicans. They wanted to use that to bargain with the Republicans for a compromise: Higher taxes elsewhere (e.g., on sales or income) and minimal spending cuts.
Now McClintock has effectively eviscerated the Democrats' bargaining position. He's told them that they can't raise the Car Tax. If they try, they still won't get any new revenues to cover this year's budget deficit, and they'll be horribly embarrassed when the voters swat them down at the next election. So their only option is to cut spending to balance the budget, and that is the thing they hate the most.