The folks at the Corner have been fretting that the enforcement provisions in the immigration bill won't ever be implemented. Looks like they have every reason to worry--businesses are now complaining that what provisions do exist will be much too onerous:

Susan R. Meisinger, president of the Society for Human Resource Management, which represents 215,000 executives, said: "The Senate proposal would require employers to reverify the identity and employment eligibility of 145 million Americans who are currently employed. That's unworkable. The burden on government and the private sector could cause the system to crash."

They're okay with enforcement, mind you, just not anything that's in danger of working. Meanwhile, high-tech industry groups are afraid that the bill's guest-worker program will give temporary-visa holders too much leverage in the labor market, while businesses that employ low-skilled workers are afraid the bill will restrict the flow of cheap labor. So they're all edging away. At this point, it's hard to see why most Republicans would risk angering the base by supporting the bill if it won't even make their campaign donors happy.

Update:suggests

--Bradford Plumer