The issue was clearly on Romney's mind as he campaigned at a factory several hours before the debate began.
"There may be some give and take. That's always entertaining," he said. "If you all could get in there we'd love to see you all there cheering."
A voice from the audience responded that there were no more tickets, and Romney replied: 'No tickets? Just storm in."
- Read: Moon Unit Newt
- Check out pictures of Obama's State of the Union address
- See the U.S. News debate on building a U.S.-Mexico border fence