Sen. Ben Nelson (D-NE), though skeptical of the "grand bargain," sounds like he will still vote for cloture. See this letter from Nelson to one of his constituents (and a helpful reader of this site)--I've italicized a telling paragraph:

Dear ------------:

Thank you for contacting me regarding Senators Kennedy and Specter's substitute
amendment #1150 to the Comprehensive Immigration Reform Act, S. 1348, also
referred to as the "Grand Bargain." I was glad to receive your thoughts.

As you may imagine, I received a significant amount of mail on the immigration
matter. I am very aware how frustrated you are, as is the case with many
Nebraskans, with this contentious issue. I, too, have shared your frustration. On
Thursday, June 7, 2007, the Senate voted on a motion to invoke cloture on the
substitute amendment (a move to end all debate and allow for a straight up-or-down
vote). The motion failed 45-50, with 60 votes needed to invoke cloture and permit
the full Senate to consider this measure. Upon failure to reach the 60-vote
threshold, Senate Majority Leader Harry Reid removed the bill from further
consideration.

It is important to remember that a cloture motion is a procedural motion, not an
actual vote expressing support or opposition to a particular piece of legislation.
While I did vote for this cloture motion for the sole reason that I believe in moving
the legislative process forward, rather than stalling it through procedural tactics, I
am glad to see this legislation withdrawn. It is my hope the Senate will now focus
on the pressing needs of border security, which I feel Congress must handle first in
order to resolve the problems of illegal immigration.

Solving the immigration issue will certainly be a complex matter; but we are in a
hole, and it is time to stop digging. Properly securing our borders first is our best
means to begin resolving this situation. This past February, I witnessed firsthand
the border barrier construction and enhanced border security measures on the
Arizona-Mexico border. Increased patrols, physical barriers and "virtual fencing" -
composed of radar, sensors, and aerial and vehicle patrols in remote areas - are
already making a difference. In addition, border patrol agents have repeatedly noted
that the assistance of National Guard members deployed through "Operation
Jumpstart" has been invaluable. Each of these elements has contributed to a
reduction in border crossings in this region, from hundreds a day last fall to a
handful a month today. I will continue to push for measures promoting efforts such
as these to ensure that we properly secure America's borders and will keep your
thoughts in mind regarding any immigration proposal which may come before the
Senate in the months ahead.

Thank you again for contacting me with your comments on this important issue.
The legislative process will only work with the input of concerned citizens, and I
encourage you to continue sharing your thoughts and ideas.

Sincerely,

Ben Nelson
U.S. Senator

A choice Sen. Nelson may have to face in the future: how much does he want to "move the legislative process forward," and how much does he wish to stop the present bill from becoming law?

UPDATE: And it may be a somewhat unorthodox legislative process that could be going forward as well.