WASHINGTON -- The New York Times reported Sunday that a newly formed super PAC supporting Donald Trump has hired veteran Republican strategist Alex Castellanos to help produce ads against Hillary Clinton .

On its face, this doesn't seem surprising. Castellanos previously advised primary candidate Mitt Romney in the 2008 presidential race. He is a staple on CNN , where he frequently opines as a conservative political commentator, and the chairman and founder of the consulting firm Purple Strategies. The super PAC he will lead, called Rebuilding America Now, is backed by real estate investor Tom Barrack, a longtime Trump friend.

What makes Castellanos latest career move so striking, however, is his past sharp attacks against the GOP's presumptive nominee.