ABC contributor Matthew Dowd previewed tonight's two important speakers - Massachusetts Senatorial candidate Elizabeth Warren and former President Bill Clinton - on the ABC News/Yahoo News DNC Live Show.

On Bill Clinton:

"I think the job of Bill Clinton is actually to present some history, and to put Barack Obama in the context of some history which he's actually the best person to do that," Dowd said. "He's going to talk about his years - balancing the budget, growth of the economy - all of those things, and then I think he's going to talk about what happened in the Bush years. And then he's going to say, 'Here's where we are today, you can choose. The path of Barack Obama is going to be much more like what I did; the path of Mitt Romney is going be much more like what George W. Bush did.'

On Elizabeth Warren:

"I think her message is much more about the people in this hall and the Democratic base. I think for her, she is more of a traditional, what you would think of as a traditional, stereotypical, what many people see as a Democrat. I don't think she helps at all with swing voters. In many ways, I think sometimes her tone and the way she is can be off-putting."