Story Corrected, h/t Leah.

After all, why should all Democrats be favored over Republicans and Independents to attend their own Democratic nominee's acceptance speech?
Also, attendees are being asked to attend early and make calls to urge people to register to vote. According to AP, "They'll be armed with data gleaned through "microtargeting" unregistered voters the campaign believes are ripe to back Obama if pressed to get on board."

From The Democratic National Convention Committee website:

"Q: Do I have to be a Democrat to receive a Community Credential? (required to attend speech and voter registration drive.) Read more…