Christine O’Donnell, the Republican Delaware Senate candidate, and her Democratic opponent, Chris Coons, hurled personal attacks at each other in a nationally televised debate Wednesday night.

A feisty, aggressive Ms. O’Donnell called Mr. Coons a Marxist whose beliefs came from a socialist professor and said he would “rubber stamp” the policies of the Democrats in Washington. Mr. Coons raised questions about whether Ms. O’Donnell’s faith would drive her positions on social issues like abortion, prayer and evolution.

Pressed by CNN anchor Wolf Blitzer, Ms. O’Donnell refused to say whether she believed evolution was a myth, saying that “what I believe is irrelevant.” As she did throughout the first half of the debate, Ms. O’Donnell quickly tried to return the focus to Mr. Coons, saying, “I would argue there are more people who support my Catholic faith than his Marxist belief.”

Mr. Coons responded that the source of her charge – an article he wrote as a student – was “a joke” that his Republican friends at the time conceived when he registered as a Democrat.

“I am not now nor have I been anything but a clean-shaven capitalist,” Mr. Coons said.