Before the debate, O'Donnell appeared to lower expectations for her performance, calling Coons a "two-time national debate champion" and "a gifted and experienced orator."
But O'Donnell quickly moved beyond early shows of nervousness to persistently and confidently make her points. Coons at several points accused O'Donnell of distorting the facts and drowning out the conversation with her "diatribes."
O'Donnell trails Coons by 19 points in the latest CNN/Time poll released today.
O'Donnell has captivated the political world in the month since she defeated Republican establishment favorite Rep. Mike Castle in the Delaware primary, raising more than $3 million from supporters nationwide.
But O'Donnell has also drawn intense public scrutiny of her personal finances and provocative past statements that have led some voters to question her suitability for office.
"I am not a witch ... I am you," O'Donnell said in one recent campaign ad -- a line which drew a sharp rebuke from Coons. "She's not me, and she's not Delaware," Coons said on ABC News' "Top Line" Wednesday.
Coons is believed to have the strongest support in the northern portions of Delaware, including New Castle County, where he leads the local government as county executive.
O'Donnell's supporters are dominant in the rural farm towns of Sussex, the southernmost of Delaware's three counties, where her campaign signs populate the country roads that run past farmers' markets and lead to the shore.
"Christine O'Donnell's the way I'm gonna go," said Clayton Townsend, a 53-year-old propane distributor in Georgetown, the seat of Sussex County. "Chris Coons is just another typical Democrat who likes to tax and spend, and I'm just not going to tolerate that."
"I just think she's a down to earth person," Townsend said of O'Donnell. "She's coming from nothing, which is basically how I built my life, from nothing."
But Sussex is not entirely friendly territory for the political novice, O'Donnell.
"I'm not a Christine O'Donnell fan," said Maria Brittingham, 43. "I've heard that she was not using her money properly, that she was using it for her own personal business."
"I hope tonight's debate is a debacle. I hope she impales herself," said a Coons supporter who would not give her name. The woman said O'Donnell's victory in the Republican primary over long-serving congressman Mike Castle has made Delaware a "laughing stock."
Castle announced Wednesday that he would not endorse O'Donnell or any candidate in the race. "There were some personal issues and other aspects of my primary campaign that were very disquieting," Castle told NPR. "And for that reason I think [it] best just to leaving it alone."
O'Donnell and Coons will face off again tomorrow in a lunchtime debate at the Rotary Club of Wilmington, according to the Associated Press. They are also scheduled to debate at Widener University Law School on Oct. 19.