Defending champion Vingegaard leads two-time winner Pogacar by 10 seconds, one of the slimmest margins after two weeks of racing, after both riders kept close to each other in the mountains, gaining only small amounts of time here and there.
On the climbs, Vingegaard has been Pogacar's shadow in the second week, being dropped only briefly on the Col de Joux Plane, and the two men rolled over the line together in Sunday's trek to Saint Gervais.
On Tuesday, Jumbo-Visma rider Vingegaard will start two minutes after Pogacar for a 22.4km effort featuring the lung-busting Cote de Domancy (2.5km at 9.4%) with Mont Blanc, Europe's highest mountain, in the background.
They are unlikely to finish with the same time and Vingegaard has been tipped to extend his overall lead over his UAE Team Emirates rival.
"I think he will take 27 seconds," former Team Sky rider Ian Boswell told Reuters in a bold assessment.
"Jumbo-Visma have better (time trial) equipment and Pogacar is a rider with instinct, flair. None of that is needed in a time trial. Vingegaard will just do his thing."
Last year, in the Tour's final time trial, Vingegaard beat Pogacar by nine seconds over 40.4km.
The overall gap will still, however, be limited after Tuesday's 16th stage and the Tour will likely be decided either in Wednesday's awe-inspiring stage to Courchevel or on the penultimate day on a brutal, hilly stage.
"It's going to be a super hard week," Pogacar told a news conference on Monday on the race's second rest day.
"Wednesday's stage is the hardest of this Tour but depending on what the riders want to do the 20th could actually be the hardest. If we still need to gain some time we'll have to attack early."
Pogacar has been the most aggressive rider, although he has learned to spare some energy after saying last year he made mistakes in failing to control his attacking side.
"I did some stupid things last year," he said.
The 24-year-old Slovenian might, though, need to finish the Tour in full swashbuckling mode if he loses time on Tuesday.
"It's like a boxing fight. I don't know if it'll come down to points, or maybe a knockout at the end but in any case it's got mouth-watering, that's for sure," said Tour de France director Christian Prudhomme.
"I think it can also be a psychological war but at the end of the day everyone focuses on themselves and when I see Jonas, he doesn't look too nervous," Pogacar said.
Pogacar broke a wrist in April and his preparations for the Tour were hampered but the injury is now behind him even if some questions about his ability to sustain his level of performance for another week remain.
"I still feel a bit of pain but the legs are good, that's what matters and I don't think the lack of racing (before the Tour) is a problem any more," he said.