SIOUX FALLS, S.D. (AP) — South Dakota's Libertarian Party is suing Secretary of State Jason Gant to try to get its candidate for Public Utilities Commission on the November ballot.

The lawsuit was filed Monday in U.S. District Court, asking a judge to put Ryan Gaddy on the Nov. 4 general election ballot.

Gant last week ruled Gaddy ineligible to run. He said Gaddy did not comply with a state law that requires candidates to be members of the party that nominates them.

Gant said Gaddy changed his party affiliation from Republican at the Libertarian convention, and the paperwork wasn't filed until later. Gant said that meant Gaddy was still a Republican at the time of his Libertarian nomination.

The Libertarian lawsuit argues that the law is unconstitutional.

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