Greenwood tells UtahPolicy.com he made the decision a week after filing because of his age and his desire to spend more time with his family.
Greenwood was facing a challenge for the GOP nomination from real estate developer Mike Schultz. Greenwood felt it was likely Schultz would have forced him into a primary.
"I didn't think the delegate votes were there that would get me out of convention," says Greenwood. "I was comfortable about going to a primary and think I would do well. But, because of my age, I didn't want to fight this thing for another month and a half. That would also mean a lot of money would be spent, I didn't think there was a need for that."
There was some speculation that Greenwood was facing some anger from delegates for his vote in favor of SB 54, the compromise between "Count My Vote" and lawmakers. Greenwood denied that had any effect on his decision to withdraw.
"That vote didn't factor into my decision at all," he said.
Greenwood was appointed to his seat in 2007 to replace Gregg Buxton who resigned to take a position as director of the Division of Facilities Construction and Management of Utah.