I don’t know but its a stupid move on his part. Even Debbie Stabenow voted no on amnesty last time around.
It's going to take several Dims in opposition to amnesty to defeat it. McCain, Graham and Kyl will all support amnesty (unless Kyl flip flops again and opposes it). Several Dims opposed it in 2006 and 2007, but there are even more of them now.
Some people say this has no chance because it's an election year. I hope they're right, but am not so sure.