Before Bill Clinton gave his speech at the Democratic convention, reports came out that Democrats were wringing their hands because Clinton hadn't submitted his speech for vetting yet (not that it mattered, he put everything back into his speech they eventually removed anyway) and they were nervous about what he would say.
Silly people. At the time, I said they were worried about the wrong thing. He would say what he was supposed to and he would do it well. He did and he did. The problem I saw was that people who remembered the Clinton presidency would compare Clinton to Obama and in that comparison, Clinton would shine, Obama would not.
In summary, Bill Clinton worked with a Congress completely controlled by the opposite party, Republicans, while Barack Obama spent his first two years in office with a Congress completely controlled by his own party. Clinton outperformed Obama, despite that handicap, in every single measure of success, from economic growth to lowering unemployment, to balancing the budget to cutting spending and public debt, lowering welfare rolls and decreasing poverty levels, etc...
Democrats shouldn't be worried about what Bill Clinton will say, they should be terrified that those old enough to remember the Clinton presidency will compare what Clinton did with what Obama didn't do. Contrast what Clinton was capable of with Obama's performance showing only what he has been incapable of.
(Full comparison piece here)
Pew Research has published their results from the Democratic convention, which shows Clinton outshined and overshadowed Obama.
What is especially interesting from the chart Pew has up, shown below, is that among all watchers, not only did Clinton do far better than Obama, but Mitt Romney also beat Obama by a point and among party faithfuls, Romney also held a one point advantage over Obama.