Joe Lieberman has never been an electrifying speaker, but his speech tonight sounded particularly flat—which makes sense, since he was kind of backed into a corner. What he wanted to emphasize was the maverick angle: John McCain puts principle over party, yadda yadda. But the best examples Lieberman had on hand—campaign finance reform, immigration, the "Gang of 14" compromise on judicial nominees—are still sore points with the conservative base, which meant that he couldn't really dig in: It's not like he was going to remind everyone how McCain once pissed off Rush Limbaugh by backing amnesty for illegal immigrants.
In any case, McCain has heaved most of his one-time contrarianism overboard. He had a nomination to win, after all. So the maverick storyline is a tough sell—the best option is to dance around it it with airy platitudes, which is what Lieberman did. Maybe that will still play well independents, or whoever on earth might find still Lieberman avuncular and reassuring, but it's a much harder message to make compelling—especially at a convention—than "ready to lead," which I'd assumed was the intended focus before Sarah Palin came along.