Genie, the 2004 keynote speech was, it is agreed, 'largely' Obamas and took several months to write.

'As for what the speakers say — well that's also careful stagecraft.
The main task for most speakers is to offer a simple biographical introduction to a large national audience. The introduction is as much about introducing viewers to the party as it is to any one speaker.
According to political historian Costas Panagopoulos, "For the 10 to 15 percent of Americans who casually pay attention to politics, this is when you put your best foot forward and your best argument."

The national convention committees review the speeches of all selected speakers, big names and small.

Leading up to the 2004 DNC, some 200 separate speeches were vetted in the speechwriting "boiler room," A similar process exists for the GOP. The speechwriters are looking for consistency with the overall message and a lack of repetition or overlap with other speakers or the nominee. Depending on the quality of the original text, speechwriters can edit liberally, adding rhetorical touches or specific information about the convention nominee, or (as with Obama's 2004 speech) they may leave the speeches largely untouched'

Dayo Olopade writing on keynote speeches last month

This time around however Obama hasn't had the luxury of time

As his top strategist David Axelrod stated "The difference here is, you know, he's got a few other things going,"

His notes have therefore been "circulated to a close group of advisers, including Axelrod and Obama's speechwriter Jon Favreau — a 27-year-old wunderkind wordsmith."