The penultime stage of the three-week grand tour of more than 3,300km and 83 hours of racing will decide the race winner with Primož Roglič (Jumbo-Visma) holding a 57 second advantage over his nearest challenger, fellow Slovenian Tadej Pogačar (UAE Team Emirates).
However, the focus for the man in third on the general classification, Colombia's Miguel Angel Lopez (Astana), is likely to be on defending his place against challenges from Aussie Porte (Trek–Segafredo) and Spaniards Mikel Landa (Bahrain-McLaren) and Enric Mas (Movistar).
Porte finished Friday's stage in the peloton along with all the other overall contenders, more than seven minutes behind winner Soren Kragh Andersen.
Meanwhile, Australian star Caleb Ewan - who has two stage wins already this year - is fifth in the sprinters' classification with his attention squarely on victory on Sunday night (AEST) on the Champs-Élysées, which he managed in 2019.
But on Saturday night (AEST), all the attention during the 36.2km individual time trial, uphill trek from Lure to La Planches-des-Belles-Filles will be on those at the pointy end chasing overall honours - with Aussie eyes fixed on Porte. P
At his best, Porte can be competitive with the likes of Roglič. You would expect that he'll need to do that here and then hope that López is not on one of his good days.
"I am feeling good. Today was a good day, and I'm looking forward to tomorrow," Roglič said at the end of Stage 19.
"Tomorrow it's all on me. The team has done an amazing job, I have the (yellow) jersey but we have all worked for it.
"I'm still relaxed. So far so good. I just have to take it in the moment. I just have to do my job."
The 2020 Tour de France continues with Stage 20's 36.2km individual time trial from Lure to La Planche des Belles Filles, a race against time for Australian Richie Porte to find 99 seconds and the third step on the Paris podium. Watch on SBS and SBS On Demand from 8:30pm (AEST) and the SBS ŠKODA Tour Tracker from 8:50pm (AEST).