Joni Ernst, the Republican nominee for U.S. Senate in Iowa, appears to believe states can nullify federal laws. In a video obtained by The Daily Beast, Ernst said on September 13, 2013 at a forum held by the Iowa Faith & Freedom Coalition that Congress should not pass any laws “that the states would consider nullifying.”

“You know we have talked about this at the state legislature before, nullification. But, bottom line is, as U.S. Senator why should we be passing laws that the states are considering nullifying? Bottom line: our legislators at the federal level should not be passing those laws. We’re right…we’ve gone 200-plus years of federal legislators going against the Tenth Amendment’s states’ rights. We are way overstepping bounds as federal legislators. So, bottom line, no we should not be passing laws as federal legislators—as senators or congressman—that the states would even consider nullifying. Bottom line.”

Ernst, a first-term state senator, has never explicitly supported pro-nullification legislation in her time in the Iowa state senate. However, she co-sponsored a resolution that says “the State of Iowa hereby claims sovereignty under the Tenth Amendment to the Constitution of the United States over all powers not otherwise enumerated and granted to the federal government by the Constitution of the United States.” It was introduced in response to “many federal mandates [that] are directly in violation of the Tenth Amendment to the Constitution of the United States."

States cannot nullify federal laws, of course.

In embracing the concept of nullification, Ernst harkens back to a discredited theory that the Constitution is a compact and states are free to void federal laws that they dislike. This view was widely promoted by John Calhoun, the great Southern advocate of slavery, prior to the Civil War and was touted by segregationists in the 1950s and 1960s. In recent years, the idea was purged of its most racist overtones and fringe elements of the right adopted it as an argument against Obamacare, gun control, and other federal regulations.

As Erwin Chemerinsky, a noted constitutional law scholar and Dean of the University of California, Irvine Law School, told The Daily Beast, nullification is expressly forbidden under 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.” Chemerinsky also noted that the Supreme Court had dealt with this issue as recently as 1958, when in Cooper v. Aaron, a unanimous decision signed by every justice on the court, it was made clear that states could not nullify federal laws or Supreme Court decisions.

Chemerinsky did point out that while “constitutional law doesn’t back up her rhetoric about the tenth amendment” in his opinion, it is something on which “people can have different views” and generally within the realm of acceptable discourse.

Historically, the Tenth Amendment has been viewed as simply a basic statement of fact rather than something that explicitly grants power to the states. The best-known description of this comes from a unanimous Supreme Court decision in 1941 by Justice Harlan Stone in United States v. Darby Lumber where Stone wrote:

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”

However, conservatives opposed to a strong federal government have pushed for a more expansive interpretation of the Tenth Amendment in recent years. Some of these, known as Tenthers, have pushed model legislation, citing the amendment, which would allow states to nullify federal gun laws.

The Ernst campaign did not return a request for comment.

A spokesman for the campaign of Ernst’s opponent, Democratic congressman Bruce Braley, said he agrees with Justice Stone’s understanding of the Tenth Amendment in Darby Lumber.

Ernst’s comments mark yet another chapter in what has been an ugly Senate campaign. Democrats have tried to depict her as an extremist and suggested that the Iowa state senator supports impeaching President Obama. In contrast, the Republicans have slammed Braley as being an out-of-touch liberal trial lawyer who is willing to sue his neighbors over minor squabbles and who looks down on those without advanced degrees.

The race is currently considered a tossup by outside observers and polling has Ernst and Braley in a dead heat.