MINNEAPOLIS -- Connecticut Sen. Joe Lieberman, a self-described Independent Democrat, headlined the Republican convention last night. Today, during a panel discussion with other policy advisers to McCain, Lieberman explained how the Democrats' vice presidential nominee in 2000 could endorse a Republican for president in 2008.

"Now, obviously part of it is John McCain," Lieberman said at the The Hubert H. Humphrey Institute for Public Affairs on the University of Minnesota campus. "But part of it is that on some criticial issues to me -- and I think to our country -- the Democratic Party has changed."

Noting the name on the building the panel was taking place, Lieberman said somewhat in jest: "If Hubert Humphrey were still a leader in the Democratic Party, I would not be at this convention."

The panel discussion focused primarily on trade issues, as Lieberman was joined by former Ohio congressman and U.S. trade representative Rob Portman, Ambassador Richard Williamson and former National Security Adviser Robert "Bud" McFarlane. When discussing Obama and Clinton's statements on NAFTA and other trade policies during the Democratic primaries, Lieberman stopped himself from saying how damaging he thought the Democratic nominee's policies could be to the economy.

"If Senator Obama really follows through on some of the things he's said," Lieberman said, "I think those anti-trade policies will have the net effect of putting this country -- I don't want to be an alarmist -- but putting us into a lot worse shape economically than we otherwise would be. Let me be as diplomatic as that."