One of the keys to immigration reform, if it’s going to pass, is that the Senate bill has to pass with some fat still on the bone. There needs to be some things that the Dems can give up in negotiations with the House, which means that they can’t agree to them now as the bill winds its way through the Senate. I don’t know if the Cornyn Amendment is a true deal killer or not. Perhaps a slightly softened version of it could provide the key to a completed bill that can pass both Houses.
In this sense, passing the Senate bill with 63 or 64 votes without adopting the Cornyn Amendment is probably preferable to passing it with the Cornyn Amendment and 70 votes. Simply put, the bill cannot be weakened much further on the pathway to citizenship without Democrats walking away from the table, but it is probably not possible to hold things as they are.
