Richard Carapaz closed in on his first Giro d'Italia triumph on Saturday after keeping hold of the leader's pink jersey in a tumultuous 20th and penultimate stage that saw Miguel Angel Lopez lash out at a spectator who knocked him over.
Ecuadorian Carapaz gave nothing to his rivals on the summit finish at Monte
Avena after the 193km ride through the northern Dolomites mountains where Astana rider Pello Bilbao snatched the stage victory.
Movistar rider Carapaz, whose expected Giro win would be his first Grand Tour victory, even helped teammate Mikel Landa in the final climb before the Spaniard lost out to compatriot Bilbao.
Landa finished second with Carapaz fourth.
The South American leads former two-time winner Vincenzo Nibali of Italy by 1min 54sec in the overall standings -- a lead that has never been overtaken in the final time-trial stage.
Landa moved third 2min 53sec adrift at the expense of Slovenian Primoz Roglic, who is 3min 06sec adrift.
"I'm already thinking about tomorrow and that 1min 54sec gap we're holding," said Carapaz ahead of Sunday's final stage which finishes in Verona's Roman amphitheatre.
"I think it should be enough, yet anything can happen into a race. The only thing I hope from tomorrow: enjoying the day to the fullest. The entire team did a remarkable job."
It was a heated final day in the mountains. Roglic picked up a 10-second penalty after a fan pushed him for over 15 seconds along the narrow roads at Croce d'Aune.
Astana rider Lopez lashed out twice at a spectator who made him crash as he headed into the final climb at Monte Avena.
A clearly frustrated Lopez got back on another bicycle but finished in 18th position, 1min 49sec behind Spanish teammate Bilbao.
"The fans should have more respect," fumed Colombian Lopez, who is trying to defend his white jersey as the best young rider. "I am sorry for my emotions, but in the rush of the race, especially in
final of the queen stage it is hard to control it. It's pity I lost my chances today because this situation happened."
Bilbao's success, his second of this year's Giro after stage seven, was a boost for his Astana outfit after Lopez's mishap.
"My first win was special," he said. "This second is even better than the first one because it's a big mountain stage. When the GC riders caught us I thought it would be hard but they were tired too," added the Spaniard.
Carapaz, Landa and Lopez were the strongest in the main climb of the day, the Manghen Pass, where they gained up to 15 seconds on their rivals Nibali and Roglic.
A breakaway group of seven riders formed in the final two climbs with French rider Valentin Madouas attacking with 16km to go before being reeled in at the Croce d'Aune.
But Carapaz was in a generous mood up Monte Avena, the final climb of the Giro over 6.9km and with a 7.3 percent gradient.
"We've tried to win the stage with Mikel Landa as well as myself to retain the Maglia Rosa (pink jersey) but we've missed out by very little," said Carapaz.
"I knew that Carapaz would try to give the win to Mikel Landa so I followed the best wheel," said Bilbao.
Carapaz is now poised to become the first Ecudorian to win a Grand Tour after last year becoming the first to win a stage on the Giro d'Italia.
The 26-year-old would be the second rider from the Andes to win the Giro after Colombian Nairo Quintana in 2014.
"Right now I can't express how I feel," said the Ecuadorian. "These days are a sensation and a situation I haven't experienced before. My family, my wife and kids, have come over from Ecuador to live this moment together with me, and now it's only one stage left.
"I'm emotional and happy with everything the boys have done for me. It's been a spectacular Giro d'Italia from the whole team, a really tough race, yet with a spectacular performance from all members."