Now that attempts to limit the tax cut extension to incomes under $1 million, Dems in Congress have two options: Vote to extend them all, or let them all expire.
If they extend them all, then they look weak and "progressives" will heap scorn on them all, including the "AWOL Obamabush".
If they let them all expire, Republicans have vowed to filibuster everything else of substance through the end of the term. So nothing else gets done from now to Xmas. And then Republicans will claim that Democrats raised taxes on everyone, and make a big deal out of re-passing the "Republican tax cuts" next term. And so the threat to let them all expire is empty; not a threat at all, but an opportunity for the GOP.