More: Although Montana's measure was the first to reach voters directly, the state is the second overall to try the maneuver " after Hawaii, where the governor signed similar legislation in May. Rather than directly restricting political spending, both versions would remove that power from the state corporate statutes that authorize companies, trade associations, and other "artificial persons" to operate in the first place.

Supporters say the strategy is crafted to avoid clashing with the Citizens United v. FEC ruling, which held that corporate election spending is protected by the First Amendment. But business groups, GOP politicians, and other opponents insist it will crash into the "unconstitutional conditions" doctrine, which prevents states from hinging the exercise of one right on the surrender of another.