Expectations management is political game I hate. I know both sides do it, but in this particular instance, it is Matthew Dowd who is compromising his credibility.
I disagree.
This is actually a brilliant strategy. Historically, there is a pretty massive bump during the first political convention, which evens up when the second convention happens.
Now, by predicting at 15 point bump, Dowd has put the bar up way too high for the Kerry campaign. If they don't get near that number, it is going to be a nail in the Kerry coffin, because Bush will come out of the Republican convention with the traditional bump the second convention gives.
After the Republican convention, Bush will have a 5 point lead over Kerry unless Kerry has the predicted bump.