This is a political move by them hoping that they can vote for it but it doesn't pass and people will forget by the next election.
Lets hope so, because if it reaches GWB's desk, he's gonna sign it, he promised as much in 2000. If the AWB bill doesn't get a bunch of attention in the Senate, It will be killed in the house and the AWB Act will sunset and it's a win win situation politically.
I would prefer Frist never bringing the bill to the floor for debate, and it's DOA before it starts, but as we all know, politics is is a game of perception, backroom deals and manipulation.