All eyes on showdown between O'Donnell and Coons

Newark, Delaware (CNN) - "I am not a witch."

Those are usually not the first words spoken by a political candidate in their first general election campaign commercial. But this year's battle to fill the Senate seat in Delaware held for nearly four decades by Vice President Joe Biden is anything but usual, which is why Wednesday's night debate between Republican Christine O'Donnell and Democrat Chris Coons, the first showdown between the two candidates, should be 'must see TV' for anyone with even a remote interest in politics.

O'Donnell scored a major upset last month when she defeated Rep. Mike Castle to win Delaware's GOP Senate nomination. Thanks to support from the Tea Party Express, a major endorsement from former Alaska Gov. Sarah Palin, as well as the strong anti-establishment and anti-incumbent feelings among voters this year, O'Donnell topped Castle, a moderate Republican who's served nine terms in the House as the state's sole congressman, as well as eight years as governor prior to heading to Congress.

Since her primary victory, the constant unearthing of controversial and colorful comments O'Donnell made around a decade ago on cable television when she was a spokesperson for conservative causes, have kept her in the spotlight. The "I am not a witch" declaration in her first campaign ad is a response to comments she made years ago on the program "Politically Incorrect" that she "dabbled in witchcraft." Bill Maher, the host of that program, is now highlighting those old clips in his weekly HBO program "Real Time."

O'Donnell says she's "matured" since her now well-known appearances. But she acknowledged in an interview with CNN that the resurfaced clips have forced her to reinvent herself in the final weeks of the campaign.

"I haven't been embarrassed. And I'm not saying that I'm proud," O'Donnell told CNN's Jim Acosta last week. "I've matured in my faith. I've matured in my policies. Today you have a forty something woman running for office. Not a 20 year old. So that's a big difference."

The debate, which will be held at the University of Delaware in Newark, will be co-moderated by CNN's Wolf Blitzer, anchor of the Situation Room, and by longtime Delaware news anchor Nancy Karibjanian of Delaware First Media.

"Since Christine O'Donnell's surprise victory in the Delaware Republican primary, the Delaware senate race has become one of the most-watched races in the country. And Wednesday's Delaware debate has become perhaps the most anticipated debate of this election season," says CNN Political Director Sam Feist.

This is O'Donnell's third bid for the Senate, following unsuccessful attempts in 2006 and 2008. Coons, the executive of New Castle County, the state's most populous county, faced no serious opposition in the Democratic primary.

While recent polls of likely voters in Delaware indicate Coons holds a 16 to 19 point advantage, O'Donnell enjoys a lead when it comes to campaign cash, which is one reason both President Barack Obama and Biden are coming to Delaware on Friday to help Coons fundraise.

The winner in November will fill out the remaining four years of Biden's final term in the Senate. Biden stepped down from his seat after his election in November 2008 as vice president. Former Biden aide Ted Kaufman was named as an interim replacement, and is not seeking a full term. After much speculation that he would run for his father's old seat, Delaware Attorney General Beau Biden announced in late January that he would instead run for re-election as Delaware attorney general. Coon's announced days later and faced no serious opposition for the Democratic Party's nomination.

–CNN's Paul Steinhauser, Jim Acosta, and Bonnie Kapp contributed to this report