Darr was elected Lieutenant Governor on November 2, 2010. He is the youngest person to win a statewide race as a Republican in Arkansas. Prior to the election, he had never run for public office. On November 2, 2010, in the closest constitutional race, Darr defeated state senator (and former Arkansas House Speaker) Shane Broadway. Darr campaigned on the notion that he could file suit against the Patient Protection and Affordable Care Act, which would be the duty of the attorney general.
On August 12, 2013, Darr announced his candidacy for Arkansas's 4th congressional district. His candidacy was short-lived, however, as political blog Blue Hog Report published a series of posts beginning on August 20, 2013, questioning campaign expenditures from Darr's 2010 campaign for Lieutenant Governor. On August 29, 2013, Darr ended his campaign for Congress.