Darr, a Republican, said he will step down Feb. 1 in order to spare his family from the fallout and what he called the "toxic business" of politics.
"I will no longer subject my family to its hard lessons," Darr said in a written statement, CNN reported. "All my forgiveness to those who play the games and all my respect and appreciation to those who serve with class and humility."
An Arkansas state ethics commission found Darr guilty of 11 campaign-finance rules. Darr admitted to the violations and agreed to pay an $11,000 fine. He had initially refused to heed calls for his resignation from Democratic Gov. Mike Beebe and others last month, but relented this week.
Darr said in August he planned to run for Congress, CNN said, but he put his plans on hold a short time later as questions over his campaign finances began to surface.
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