Scotland’s O’Hara, who needs a top-three finish to secure his Tour card for next season, is back in a tie for eighth spot after a 74 in which he covered the first 14 holes in a sorry five over, but then birdied the final three holes.
Els dropped all the way to joint 53rd after a 76.
Otto’s 65 moved him to 14 under par. The 35-year-old, whose one European Tour victory came at the 2008 Italian Open, is now three in front of twice champion Retief Goosen, their fellow South Africans Thomas Aiken and last week’s winner Garth Mulroy and also Swede Magnus Carlsson.
Otto was four behind O’Hara at the start of the day and played the first six holes in one over, but started his charge with birdies at the seventh, eighth and tenth. An eagle on the 603-yard 11th lifted him right into the thick of the action and further birdies at the 12th, 15th and 17th made him the man to catch.
n South Korean KT Kim fired a third-round 67 to take a one-shot lead over American Bubba Watson at the Australian PGA Championship at Coolum.