Great Britain's Simon Yates extended his La Vuelta lead with a strong showing in Tuesday's individual time trial on stage 16.
Australia's Rohan Dennis won the 32-kilometres race from Santillana del Mar to Torrelavega in 37 minutes 57 seconds - 50 seconds clear of his BMC Racing team-mate Joseph Rosskopf of the United States.
Yates (Mitchelton-Scott) finished 13th, 1 minute 28 seconds behind Dennis, but crucially ahead of all bar two of his rivals for the general classification.
Holland's Steven Kruijswijk (LottoNL-Jumbo) was fourth on the stage, 37secs ahead of Yates, and Spain's Enric Mas (QuickStep-Floors) was sixth, 25 seconds ahead of of the Briton.
But Spain's Alejandro Valverde (Movistar) and Colombia's Nairo Quintana (Movistar) conceded seven and 42 seconds to Yates, respectively.
Dennis is not in overall contention and was targeting the stage as preparation for the Road World Championships time trial later this month.
Ireland's Nicolas Roche meanwhile crossed in 41 minutes and one second for BMC. He's 36th in the general classification.
Yates had, on Monday's rest day, attempted to downplay his chances of holding the red jersey all the way to Madrid.
But the 26-year-old Bury rider, not renowned for his talent against the clock, has a strong cushion with four days of racing remaining ahead of Sunday's processional stage in the Spanish capital.
Yates now leads from Valverde by 33secs, with Kruijswijk, who had begun the day 1:29 behind, now third, 52 seconds adrift. Quintana dropped to fourth, 1:15 behind.
Yates can expect his advantage to come under attack in Wednesday's hilly 17th stage, the 157km route from Getxo to Balcon de Bizkaia in the Basque Country.