Kentucky GOP Primary Pits Incumbent Massie Against Trump-Backed Challenger

Rep. Thomas Massie is campaigning ahead of Tuesday's Republican primary in Kentucky's 4th congressional district against a challenger endorsed by President Trump. Massie told ABC News' "This Week" on Sunday that three billionaires from outside Kentucky have funneled millions of dollars into the race.

He said the spending has made the contest the most expensive congressional primary in history. "How did this race become the most expensive race in the history of Congress for a primary? It's because three billionaires from outside of Kentucky have funneled millions of dollars in here.

They're trying to buy a seat," Massie said.

Massie identified Miriam Adelson, Paul Singer, the Republican Jewish Coalition and the American Israel Public Affairs Committee as the main sources of outside money. He described them collectively as part of the Israeli lobby and said the contest has become a referendum on whether foreign interests can dictate U.S. foreign policy.

"It will be a referendum on foreign policy — whether Israel gets to dictate that by bullying members of Congress. And I'm the one they haven't been able to bully," Massie said. President Trump has repeatedly criticized Massie on social media, calling him the worst Republican in Congress and urging voters to remove him on Tuesday.

The challenger, former Navy SEAL Ed Gallrein, received Trump's endorsement before entering the race. Trump posted that Massie voted against tax cuts, the border wall, the military and law enforcement. Massie said he remains confident because of endorsements from right-to-life and gun-rights groups plus recent grassroots donations.

He noted that four members of Congress campaigned with him in the district on Saturday. "I have the endorsement of the right to life organizations, the gun organizations. I had four members of Congress come here yesterday and campaign with me," Massie said.

ABC News has requested comment from the Republican Jewish Coalition, AIPAC, Adelson's foundation and Singer's foundation but has not yet received responses.