Don't interpret too much into "people who now say they are definitely voting in November".
This will only start getting interesting in polls 1 week after the Democratic convention.
As a reference, here is the 2004 convention bounce for Kerry and Bush:
At the end of July, after the DNC, Kerry bounced from 45.5% to 48%. The fact that Bush also bounced at that time was probably because of the 1-minute Swift Boat ad that was released at that time as well.
Then in early September, after the GOP convention, Bush went from 45.5% to 50.5%. while Kerry went from 45.5% to about 43%.
The early July bounce for Kerry was probably because he picked Edwards at this time.