Ric Grenell, who was an acting director of National Intelligence for the Trump administration, has pulled his support for Arizona GOP Senate candidate Jim Lamon, following a string of attack ads by his campaign including one on fellow conservatives PayPal co-founder Peter Thiel.

Thiel, a billionaire, is backing Blake Masters, who is competing against Lamon and several others in the GOP primary to challenge Arizona Democrat incumbent Sen. Mark Kelly in November.

“Attacking my friend Peter Thiel is a bad strategy that only helps elect Democrats” Grenell tweeted Wednesday. “Peter has been a champion of conservative values in Silicon Valley and has never wavered from challenging Big Tech.”

Masters is a friend and protégé of Thiel’s and served as chief operating officer of the Thiel Capital hedge fund and president of the Thiel Foundation.

Masters also recently received the endorsement of former President Trump.