Hagan announced the defamation suit after the Dole campaign refused to stop running the ad, which seeks to link her to an atheist group, The Hill reported. Hagan said the Dole campaign faked her voice in the ad to make voters think she doesn't believe in God.
"Elizabeth Dole's attacks on my Christian faith are offensive," Hagan said in a response ad that began airing Thursday.
Hagan, who has taught Sunday school, said she is running for office to help boost the economy and create jobs instead of "bearing false witness against fellow Christians" -- a suggestions that Dole broke one of the Ten Commandments.
"In filing this suit, we've made clear that these kind of despicable tactics will not be tolerated," Hagan spokeswoman Colleen Flanagan said in a statement, "and our campaign is moving forward with the most important task at hand: defeating Elizabeth Dole, and giving North Carolina's families a voice in the U.S. Senate that they've been sorely missing."
Dole spokesman Daniel McLagan called Hagan's response "fairly hysterical." He said it is "sad" that Hagan has "stooped that kind of name-calling" and insisted that everything in Dole's ad is true.
Hagan leads Dole 46.6 percent to 42.9 percent in the latest Pollster.com trend line of all polls taken of the North Carolina Senate race, The Hill said.
Local newspapers have condemned the Dole ad. The Greensboro News & Record said in an editorial that Dole's ad is "worse than dishonest" and called on Dole to pull it from the air.