Updated

Sen. Joe Lieberman, I-CT, would vote to start debate on the campaign finance bill known as the DISCLOSE Act, spokesman Marshall Wittman tells Fox, because "the senator supports more disclosure on campaigns."

However, Wittman said Lieberman, who is attending a family member's funeral and will miss Tuesday's vote, "cannot vote for the bill in its current form."

Wittman said the senator is "concerned about unfair treatment of businesses related to unions," a position that puts him squarely on the side of the Chamber of Commerce, which has fought hard to kill this bill.

The Schumer bill imposes stiff, new disclosure requirements on campaign spending, though it does not require organizations receiving less than $600 donations for political advertising and other campaign activities to disclose its donors.  This, according to a Schumer aide, shields small time donors who are members of unions that are politically active.