NEW: Utah’s Orrin Hatch, the longest-serving GOP senator, announces his retirement. “Every good fighter knows when to hang up the gloves,” he says in a Twitter video.

NEW: Utah's Orrin Hatch, the longest-serving GOP senator, announces his retirement. "Every good fighter knows when to hang up the gloves," he says in a Twitter video. pic.twitter.com/DoUpKeBsjf

— CBS News (@CBSNews) January 2, 2018

Source: Twitter