Italian Vincenzo Nibali took a giant step towards his maiden Giro d'Italia triumph by smashing his rivals on his way to winning a rain-soaked 18th stage uphill time trial from Mori to Polsa on Thursday.
Australian Cadel Evans began the day only 1min 26sec behind the Italian, but the 2011 Tour de France champion flattered to deceive on his way to a 25th place at 2:36 behind.
Ahead of two key mountain stages in the Dolomites, which may have to be altered depending on the severity of the wintry weather expected at high altitude, Nibali now leads Evans by 4:02.
Colombian Rigoberto Uran is third overall at 4:12 with former pink jersey winner Michele Scarponi, who is aiming for a podium finish, fourth at 5:14.
It was Nibali's first stage win of this year's race, and third overall, and should be enough to see him become the first Italian to win the Giro since Scarponi was handed the 2011 title after Alberto Contador of Spain was disqualified for doping.
"I have a significant advantage now and that will allow me to control the coming two stages in more tranquil fashion," said Nibali, who rides for the Astana team.
Nibali, the 2010 Tour of Spain winner and runner-up on the 2011 Giro d'Italia, came to this year's race extra determined having been pushed into third place by Bradley Wiggins at last year's Tour de France.
However despite being well suited to the rolling, uphill test, few expected the Italian to dominate as he did.
Nibali said after Wednesday's stage to Vicenza that Evans had been "pedalling well".
On Thursday the Italian said: "I thought he would be better today.
"But he's been hidden in the peloton in recent days so we didn't know what to expect from Evans."
When Evans passed the intermediate time check after 9.5 km he was already languishing beyond the 20th provisional place.
Nibali had started three minutes behind Evans but caught sight of the Australian at the finish.
"He was my reference point, so when I heard I was closing the gap to him it pushed me to go that bit harder."
Evans, too, thought he would be better.
"Today wasn't what I was looking for or what I was even expecting," said the Australian.
"But when you're halfway into a time trial it's not like I can find an extra minute. It's not through lack of trying that I lose a minute or two minutes."
Spaniard Samuel Sanchez set the early pace from among the big names in a time of 45:27 -- when the course was still fairly dry.
He took the provisional lead with a time that was 22secs faster than Italian Damiano Caruso but, despite heavy rain hitting the course later on, Sanchez was unceremoniously pushed into second place when Nibali, punching his arms in triumph, posted a time that was 58secs faster.
"I'm happy with my performance," said Sanchez, the 2008 Olympic champion.
"It wasn't enough to beat the pink jersey, but he's been the strongest rider here. To beat Nibali today was mission impossible."
Wiggins began the Giro as Nibali's main threat, but the Englishman, as well as Canada's defending champion Ryder Hesjedal, quit the race due to illness last week.
Evans, too, said Nibali would be a deserving winner.
"Nibali here is in a class of his own. Maybe, more than maybe, he deserves to win the Giro," added the Australian.
The race finishes on Sunday with a mainly flat 197 km stage from Riese Pio X to Brescia.