Sepp Kuss virtually clinched Vuelta a Espana victory on Saturday as he maintained his overall lead before the ceremonial finale, while Wout Poels won stage 20 in a sprint finish ahead of Remco Evenepoel.
American Jumbo-Visma rider Kuss only needs to make it through Sunday's procession through Madrid to earn his first Grand Tour triumph.
The 29-year-old, usually a member of the supporting cast for co-leaders Jonas Vingegaard, who is second overall, and Primoz Roglic, third, has held the red jersey since stage eight.
Back-to-back Tour de France winner Vingegaard and three-time Vuelta champion Roglic, who won this year's Giro d'Italia, supported their colleague's maiden success in the final stages, apparently on team orders.
Kuss leads Vingegaard by 17 seconds and Roglic by one minute and eight seconds going into the final day, a flat 101.5 kilometre ride from La Zarzuela Hippodrome to the heart of the Spanish capital.
The three riders crossed the line together, Kuss flanked by his team-mates, who slapped hands with him and patted him on the back.
"I'm super relieved, I'm still recovering from that last climb," Kuss told Eurosport.
"It was a long hard day ... Primoz did a lot of work for me on the last climb and on the flat with Jonas, and that's something I never imagined.
"(Celebrating together) was a special moment, to be able to relax that much in the last kilometre of a mountain stage with your two team-mates is really cool."
Kuss will become the first American rider to win a Grand Tour since Chris Horner won La Vuelta in 2013.
Jumbo-Visma are set to become the first team to complete an historic treble -- winning all three of the Grand Tours in a single calendar year.
No rivals challenged the Dutch team's overall dominance on a gruelling, hilly 207.8 kilometre run from Manzanares El Real to Guadarrama.
A strong early breakaway of 31 riders formed, including reigning champion Evenepoel, favourite to win the stage after already clinching the King of the Mountains jersey for best climber.
With no general classification challengers in the break, the Jumbo-Visma controlled peloton let the gap grow.
On the final climb, Bahrain Victorious rider Poels broke off the front. Lennert Van Eetvelt followed, with Marc Soler joining and Evenepoel dropped.
However, the Belgian Soudal-QuickStep rider came roaring back on the descent and, along with Pelayo Sanchez, the five riders were set for a sprint finish, won by Poels.
The Dutchman set off early on his dart to the line and Evenepoel almost caught him but could not get in front.
The 35-year-old Poels won a Vuelta stage back in 2011 and also has one Tour de France stage victory to his name.