The pro-Israel lobby has spent millions on an effort to unseat Rep. Thomas Massie in the Kentucky Republican Primary on Tuesday, making it the most expensive House primary on record. 

Pro-Israel interest groups have dropped $9 million into the effort, and prominent Republican pro-Israel donors spent millions more on a super PAC supported by President Donald Trump's political operations, which has spent $7 million on the race. Altogether, spending on the race has topped $32 million, according to Politico, which cited figures from AdImpact. 

The Republican Jewish Coalition Victory Fund and United Democracy Project, a super PAC of the American Israel Public Affairs Committee, have attacked Massie for his votes against measures supporting Israel. 

Patrick Dorton, spokesperson for United Democracy Project, called Massie "the most anti-Israel Republican in the House." Massie has said he's not against Israel. He told Politico that it's incorrect to equate criticism of the policies of Israeli Prime Minister Benjamin Netanyahu with antisemitism.