(Repeats changing slug, no changes to copy) ADELAIDE, Jan 18 (Reuters) - Richie Porte raced away from his rivals on the final climb to open a decisive 20-second lead after the second stage of the Tour Down Under on Wednesday, the Australian putting himself on course for a first victory in the event. The BMC team leader has finished second twice in the six-stage race around South Australia but with previous editions normally won by a handful of seconds, Porte's advantage will be difficult to reel in over the four remaining days. "It's incredible to wear the jersey in the biggest race in Australia," the 31-year-old Tasmanian all-rounder said after racing clear of his rivals on the 1.6 km Paracombe climb. More...