Arizona Sen. John McCain is up for re-election this year. The state's Republican primary is next week. | AP Photo McCain rips major Trump donor, warns of future campaign finance scandals

SCOTTSDALE, Ariz. — A billionaire supporting Sen. John McCain’s underdog primary opponent may be doing so as payback, McCain said Wednesday.

Robert Mercer, co-CEO of hedge fund Renaissance Technologies, gave $200,000 to a super PAC supporting Kelli Ward, McCain’s conservative challenger in next week's GOP primary. The money helped fuel a $600,000 ad campaign that alleges McCain “betrayed us on amnesty” and boosts Ward.


Two years ago, McCain and former Sen. Carl Levin (D-Mich.) issued a report that named Mercer's company as among more than a dozen firms that dodged billions in tax payments through a complicated financial product known as basket offerings. McCain said at the time that companies including Renaissance Technologies played "by a different set of rules" and secured an "unfair tax advantage over ordinary citizens.”

On Wednesday, McCain suggested there’s a connection between Mercer's financial help for Ward and the scrutiny his company's trading practices received. The senator predicted that there will be "scandals in the future" regarding campaign finance due to these shadowy connections.

“We issued a scathing report about this guy evading taxes, his firm. I’m sure there’s no connection of a $600,000 injection into the Kelli Ward campaign,” McCain said sarcastically. Mercer is a major financial backer of Donald Trump and an investor in Breitbart News, the conservative pro-Trump website.

A spokesman for Renaissance Technologies did not immediately respond to a request for comment.

McCain has his own big-money ally, Arizona Grassroots Action PAC, that’s lighting into Ward and aiding McCain to the tune of at least $2 million. The co-author of sweeping campaign finance reforms that have largely been struck down, McCain acknowledged the irony of his super PAC support.

“You’ve got to play the game by the rules, but I don’t think there’s any doubt that there will be future scandals. We’ve gone through a cycle ever since Teddy Roosevelt of corruption, reform, a period of time, corruption, reform," McCain said.

If McCain is reelected and former Sen. Russ Feingold (D-Wis.) beats incumbent Wisconsin GOP Sen. Ron Johnson, there could be an opportunity to rewrite campaign finance laws in 2017. But McCain said that there will need to be an impetus to do so.

“It depends on the environment. It’s gotta be ready. One of the major reasons we were able to do McCain-Feingold was the Abramoff scandal. There’s gotta be some kind of catalyst. Right now all the politicians are happy with a super PAC and the status quo,” McCain said. “But there will be a scandal. That’s history. And it does repeat himself.”