You'll need to launch a media campaign to win coverage for your event. Begin with a well-crafted press release that underscores the reason for the event and names the dignitaries who will appear.

Send it to your press list by fax or e-mail, and then follow up by phone.  Stress the need for the event and pitch a larger story to key journalists. 

You can also get a member of the media involved as the master of ceremonies to ensure more coverage. Just be sure the media person is from a major press outlet that will reach the right people for you. 

Send out a second release closer to the date that publicizes the event from a slightly different angle, and follow that up with phone calls as well.

In addition, you can put together a support team and give each person a certain number of tickets to sell.  Talk with local businesses about buying tables or taking sponsorships and acknowledge them in your program.  Good luck!