Brand dilution

Obama has sold his campaign, as being about bringing real change to Washington, or change we can believe in. This is unsurprising, in the U.S., challengers always seem to run on bringing change to the corrupt culture of Washington. But he seems to have convinced a good number of people that he's not just saying it. If I'm right that he has convinced people of this, shouldn't his campaign be worried about claiming that every Democrat running for office is part of that real change? Surely some of them aren't, and it gets harder to believe that any of them actually represent real change I can believe in when it's claimed that all of them do.