"We'd like to give grassroots supporters an opportunity to join in the fun," first lady Michelle Obama wrote in an email. "You guys deserve it, and I know Barack would personally love to see you there. Donate $3 or whatever you can today, and you'll be automatically entered to get your name added to the guest list."
Winners will also get round-trip airfare and hotel accommodations in Chicago.
To be eligible, candidates must be U.S. citizens or lawfully admitted permanent residents and the contribution must come from an individual over the age of 16. Read more about the details here. A donation is not required for entry.
The deadline is Thursday, July 26.