problems getting their tax bill passed tonight. let's go to sunlen serfaty. she's on capitol hill tonight. what's the latest? what is happening? >> unexpected drama here in the senate, showing how delicate these negotiations over the republican tax plan are happening. i'll show you some pictures. this happened on the senate floor. this should have been a simple procedural vote, a democratic amendment that would have sent the bill back to committee for three days. republicans should have voted that down very easily. rather than being voted down, though, by republicans, the floor was held open for an hour where you saw this remarkable huddle and the senate majority leader, the number two and three in the sfenate huddling around jeff flake and bob corker. they have been raising big issues over the deficit and we're told, according to a source that told my colleague phil mattingly, this centers around the so-called deficit trigger.