TIME’s Swampland: The Arizonan’s economic adviser tells Fortune columnist Matt Miller in his upcoming book that higher taxes are inevitable — adding, “it’s arithmetic.”

“If you do nothing on the spending side, you’re going to have to raise taxes whether you’re a Republican, a Democrat or a Martian.”

Asked why Republicans still insist they’ll cut taxes, he says, “It’s the brand, and you don’t dilute the brand.”