The candidates will be speaking to a TV audience of tens of millions in one of those rare moments when a critical mass of Americans collectively fix their attention on one event. Fifty-two million people tuned in to the first debate four years ago, and 80 percent of the nation's adults reported watching at least a bit of the debates between Obama and Republican John McCain in 2008.
The two campaigns on Wednesday announced new websites — http://debates.mittromney.com and http://barackobama.com/debate — to respond to their opponent in real time.
In a quadrennial pre-debate ritual, each campaign has worked overtime to raise expectations for the opponent while lowering the bar for its own candidate. The thinking is that it's better to exceed lukewarm expectations than to fail to perform at an anticipated level of great skill.
But both men are seasoned debaters: Obama has been here before, facing off with McCain in 2008. Romney hasn't gone one on one in a presidential debate, but he got plenty of practice thinking on his feet during 19 multicandidate debates held during the Republican primaries.
On a long day of debate prep — Romney in Denver and Obama in Henderson, Nev., near Las Vegas — both candidates tried to blow off some steam Tuesday. The president made a tourist's visit to nearby Hoover Dam, and Romney fit in a lunchtime outing to a Mexican grill for a burrito bowl.
The two candidates' biggest fans talked up their debating abilities in pre-debate interviews.
Michelle Obama told CNN she's like a nervous parent watching a child performing on the balance beam when her husband debates.
"I do tell him to have fun and relax and just be himself, because the truth is, if he's the Barack Obama the country has come to know and trust, he is going to do a great job," she said.