Ernst, a Republican, was caught espousing wishful thinking as policy in a September 2013 forum held by the Iowa Faith & Freedom Coalition, saying Congress should not pass laws "that the states would consider nullifying."
In a video of the event obtained by the Daily Beast, Ernst describes "200-plus years of federal legislators going against the Tenth Amendment's states' rights."
"We are way overstepping bounds as federal legislators," she said. "So, bottom line, no we should not be passing laws as federal legislators -- as senators or congressman -- that states would even consider nullifying."
Unfortunately for Ernst, Supreme Court case law has determined the Constitution actually forbids nullification, and interprets the Tenth Amendment as a basic statement, not a prohibition against the federal government from passing additional laws not already enumerated.
In the 1958 case Cooper v. Aaron, the justices unanimously said states could not nullify federal laws or Supreme Court decisions, as forbidden in Article VI of the Constitution: "This Constitution, and the Laws of the United States which shall be made in Pursuance thereof... shall be the supreme Law of the Land."
And in 1941, the court unanimously upheld a limited Tenth Amendment interpretation in United States v. Darby Lumber:
The amendment states but a truism that all is retained which has not been surrendered. There is nothing in the history of its adoption to suggest that it was more than declaratory of the relationship between the national and state governments as it had been established by the Constitution before the amendment or that its purpose was other than to allay fears that the new national government might seek to exercise powers not granted, and that the states might not be able to exercise fully their reserved powers."
"Tentherism" was one of the primary justifications used by pro-slavery advocate John Calhoun in the years leading up to the Civil War, and a hundred years later, by segregationists opposing civil rights. More recently, conservatives have resurrected the theory to argue for nullification of federal gun laws, the Affordable Care Act and other federal regulations.
The Iowa race for retiring Sen. Tom Harkin's seat, was once thought to be an easy seat for Democrats to retain. But gaffes by nominee Bruce Braley, a trial lawyer, paved the way for a surging Ernst, who easily won the Republican nomination. Recent polling shows the race in a statistical tie.
UPI has reached out to the Ernst campaign for comment.