South Dakota appears to be the only state in the nation to impose a law seeking to ban money from outside its borders for ballot question races, but the future of the new voter-approved measure is uncertain as critics expect it to be challenged in court.

The ballot question easily passed Tuesday in an election that also saw voters approve an initiative to require constitutional amendments to stick to a single subject.

House Speaker Mark Mickelson spearheaded both initiatives. He says the new measures and rules passed earlier this year would make out-of-state interests that have dumped a deluge of money into South Dakota campaigns turn elsewhere.

But Don Haggar, state director of Americans for Prosperity-South Dakota, says he expects the out-of-state money ban to be overturned, calling it "clearly unconstitutional."

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