Simon Gerrans is on the verge of making Tour Down Under history after beating fellow Australian cycling star Cadel Evans in an epic duel on Saturday.
Gerrans finished third in the decisive fifth stage at Willunga south of Adelaide to take the lead from Evans by just one second.
Evans (BMC) lost his seven-second overall lead when Gerrans and Italian Diego Ulissi attacked him in the last few hundred metres of the 151km stage.
Gerrans' Orica-GreenEDGE team will now try to cap off a week of outstanding work by protecting his narrow advantage in Sunday's final stage, a street race through the Adelaide CBD.
Gerrans, the 2006 and 2012 champion, will be the first rider in the Tour's 15-year history to win three titles if he can keep his lead.
Richie Porte, the other big Australian rider in this race along with Gerrans and Evans, was masterful on the Old Willunga Hill climb and won the stage.
The Sky rider finished 10 seconds clear of Ulissi and Gerrans, while Evans was sixth at 14 seconds.
Ulissi (Lampre) lies third overall at five seconds and Porte jumped from 11th to fourth at 10 seconds.
"It's not only a huge thrill, it's a huge sigh of relief," Gerrans said.
"My whole team has put in such a huge effort to support me this week.
"I'm so thrilled to have the lead back going into the last stage."
Gerrans led after winning stage one, but lost it when Evans rode brilliantly to win stage three.
"Not an ideal result today - beaten by better team. Compliments OGE (Orica-GreenEDGE)," Evans said on Twitter.
As expected, the stage came down to the last of two 3.5km climbs up Old Willunga Hill Rd to the summit finish.
Evans and his BMC team attacked at the foot of the climb, putting Gerrans into difficulty.
But Gerrans, who has a second place and a win at Willunga since the stage became a summit finish, used his local knowledge well.
He also had vital support from teammates Simon Clarke and Daryl Impey as they pegged back Evans' initial break.
Porte jumped clear with 2km left and no one could go with him.
"I saw Cadel did a heck of a lot of work on the earlier slopes of the climb and I knew he'd pay for that in the final," Gerrans said.
"When Ulissi and I jumped for the line, we obviously put a pretty good gap into Cadel."
A one-second lead may not look like much, but Gerrans was equal on time with Spaniard Alejandro Valverde after Willunga two years ago when he won his second title.
Orica-GreenEDGE director Matt White is supremely confident they can successfully monitor Evans and Ulissi through the two intermediate sprints in Sunday's stage and then the finish.
The two sprints and the finish all feature crucial time bonuses.
"One second - four minutes. It doesn't matter," White said.