The 2019 world champion managed to pull a further 3.0s clear of Hyundai rival Craig Breen to lead the Irishman by 11.2s with two stages remaining at the snow rally.
Equipped with fresh studded tyres, Tanak was able to clock the second fastest time on Stage 16 (Vastervik, 26.4km), while Breen, utilising a mix of new and worn tyres, was only able to post a time good enough for fourth.
Tanak's effort came despite the Estonian battling with the brakes on his Ford Puma during the stage, while Breen admitted he had been too cautious at times as his hopes of a maiden WRC victory continued to fade.
"I tried to be as committed as I could, but in one or two places I was just too hesitant,” said Breen. "We got through it cleanly with no mistakes and that's very important.”
The fight for the final podium spot took another twist as world champion Kalle Rovanpera took a chunk of time out of Hyundai's Thierry Neuville.
The Toyota driver notched up his sixth stage win of the event as he whittled the gap to third-placed Neuville down to 1.1s.
Rovanpera’s morning didn’t get off to the best of starts as the Finn revealed he encountered a “small issue” on the road section before the stage.
"Quite happy. On the narrow section I could have been a bit cleaner, but I have been struggling all weekend on the narrow technical sections," said Rovanpera.
“We had a small issue on the road section, it was a bit of a mess, but finally everything was fine on the stage. It was nothing too big.”
Neuville confirmed that he had only been running on two new tyres as he prepared to save his fresh rubber for the final two stages, following the morning service.
Toyota’s Elfyn Evans safely completed the stage but dropped 16.2s which the left the Welshman a distant fifth, 1m12.4s adrift of the lead.
M-Sport’s Pierre-Louis Loubet headed to the final service in sixth, with Oliver Solberg seventh overall and leading WRC2 by 45.7s from Ole Christian Veiby.
