MADISON, Wis.- House Speaker Paul Ryan's Republican primary challenger told a columnist for the New York Post in a Twitter message to "Eat a bullet."

Paul Nehlen sent the tweet on Wednesday night. It came after a back and forth with Post columnist John Podhoretz that stemmed from a tweet Nehlen sent about a bill passed by the House that would make it easier for gun owners to legally carry concealed weapons across state lines.

Podhoretz tweeted to Nehlen: "Maybe you should eat something. Your brain needs nourishment. It's the size of a pea."

Nehlen tweeted in response: "Do us all a favor, Podhoretz. Eat a bullet."

Nehlen did not immediately respond to a message seeking comment Thursday.

Nehlen ran against Ryan in 2016 and got 16 percent of the vote.