"If Al Franken comes on board" and gives the Democrats a filibuster proof majority, he said, "there will be 60 members of the caucus, not an 60 automatic votes."
"Having Arlen there, maybe I'll have somebody to share the penalty box with me from time to time," Nelson quipped.
The senator later told host Bob Schieffer he was not entirely serious.
"I'm more joking about the penalty box, I'm never in the penalty box," Nelson said. "People in our caucus, the people of Nebraska, know that I'm an independent-minded person, and that's one of the reasons I think they've sent me there, it's one of the reasons I get along with my colleagues in the Democratic caucus."
Watch the interview below. It opens this week's edition of "Washington Unplugged," CBSNews.com's 15-minute Web-only show, which also includes a journalist roundtable on Specter's move to the Democratic Party and a chat with the New York Times reporter who asked Mr. Obama an "enchanting" question at Wednesday's press conference.