Backgrounder

The original Bush tax cuts were passed under budget reconciliation, because the Republicans thought that didn't have enough votes to end a filibuster.  As it turned out, they got more than 60 votes for the tax cut. Nevertheless, the reason the tax cuts are expiring is because they were enacted under reconciliation.

Why can't the Democrats do the same thing?  The Senate did, after all, have 53 votes to pass a version in which some of the tax cuts at the top end are allowed to expire, and the House already passed a similar measure. Why couldn't the Democrats do what the Republicans did ten years ago?

Because you can't have budget reconciliation if you don't pass a budget first.