If no bill comes out, Senators who voted no for the current Senate bill will claim they were protecting their voters from a bad bill, and Senators who voted for the current Senate bill will claim they did what they could to get a fix to the immigration problem rolling. Of course immigration is a national issue, but as we've already touched on, Congressional politics are local, and the Senators already voted with their constituents in mind. The calculations have already been done. I fully expect no immigration bill will pass this year. But that doesn't matter in Congressional elections decided at the local level.
All of the House is up for election and only one third of the Senate. Illegal immigration will be an issue in many of the races. Depending upon the district or state, the challengers will try to use the issue against the incumbent. Both the Senate and the House members have voted with their constituencies in mind. Others like McCain, Hagel, and others see it as an issue for 2008. They are pandering to the growing Hispanic vote.
Kate O'Beirne makes a good point. More Senate Reps voted against the bill than voted for it and the same is true for the House bill, which is not supported by the WH. We have a situation where the majority of Reps in Congress don't support the WH and vice versa.