The 90-minute exchange at the University of Denver starts at 8 p.m.
The debate will be broadcast on the major television and cable news networks.
Some things to watch for:
Goals for Romney
Be aggressive but friendly
Make Obama the issue
Goals for Obama
Defend record without appearing defensive or irritable
Use humor -- but off the cuff, not canned "zingers"
Obama is in trouble if:
He can't explain why we've borrowed $5 trillion and unemployment is still above 8 percent.
Romney is in trouble if:
He can't explain why requiring health insurance is good in Massachusetts but bad everywhere else.
* * Who faces the bigger challenge?
Romney. He's close but still behind in most public opinion polls. He needs to convince any remaining persuadable voters to take another look at his candidacy.
Who has the most to lose?
Obama. Protecting a small lead is one of the toughest jobs in politics -- a mistake or a too-sarcastic response could bring Romney fully back into the race.
Dave Helling, email@example.com.
Debates aren't what they used to be. | A4
Economy will be big issue. | A7