Lando Norris' second place finish, behind Mexican Grand Prix winner Carlos Sainz. cut Max Verstappen's world championship lead by 10 points after the Red Bull driver was handed 20 seconds in penalties as he forced his title rival off the track in a dramatic race.
Norris drove a brilliant final stint to finish second in Mexico City, behind Sainz but crucially four places ahead of Verstappen as he cut the lead to 47 points with four races remaining and 120 points to play for.
Norris was demoted behind Verstappen after being penalised for overtaking his rival off the track in Austin last time out, with the controversial incident dominating the agenda throughout this weekend.
McLaren challenged that five-second penalty as they arrived in Mexico, claiming that Norris was ahead and Verstappen had forced him off the track, but the stewards rejected their right of review.
The title protagonists came together again just 10 laps in at the Autodromo Hermanos Rodriguez as Norris was forced to leave the track twice within three corners.
Verstappen forced Norris wide at turn five before charging into turn eight, running Norris off the track and staying ahead as the McLaren man skirted with the wall.
On this occasion the stewards agreed that the Dutchman was in the wrong. The championship leader was initially handed a 10-second penalty for forcing Norris off the track at turn five.
"Ten!? That's quite impressive," Verstappen said over the radio.
His race engineer Gian-Piero Lambiase replied: "There was a lot of whinging. A lot."
But it soon got a whole lot worse for the three-time world champion as the stewards punished him with another 10-second penalty for gaining an advantage by leaving the track at turn eight.
Norris said after the race: "It was a tough race. A lot of the first few laps was trying to stay in the race and avoid any crashes.
"I knew what to expect (from Max). I didn't want to expect such a thing because I respect Max as a driver.
"Not very clean driving but I avoided him."
Norris had started third, a place behind his championship rival, on the 768-metre blast down to turn one – the longest on the Formula One calendar.
Verstappen got the better start, quickly jumping ahead of pole-sitter Sainz.
Norris had got a good slipstream behind the leading pair but could find no way through and the battle was soon neutralised by a safety car after a heavy first-corner collision between Yuki Tsunoda and Alex Albon – with both drivers retiring from the race.
The Mexican crowd have roared on Sergio Perez all weekend, despite the under-pressure Red Bull driver qualifying only a lowly 18th.
He surged up to 13th by the time the safety car was called but, to add further misery to the man who this week labelled his season as "terrible", he was handed a five-second penalty for a false start after beginning outside his grid box.
The race resumed on lap seven as Verstappen comfortably retained his advantage but Sainz remained with DRS range and just two laps later used it to sling up the inside at turn one and regain the lead.
But that was only the start of the drama as next time around Norris and Verstappen came together.
"I was ahead the whole way through the corner." Norris said over the radio.
"This guy is dangerous. It's the same as last time. I'll be in the wall in a minute."
The stewards agreed with Norris, handing Verstappen his 20 seconds of penalties.
Austin race winner Leclerc passed the pair of them during the drama to move up to second.
Verstappen pitted and served his 20-second penalty on lap 27, dropping from third to 15th and over 41 seconds behind Norris.
The Red Bull man soon charged back up to finish sixth, however, as he attempted to limit the damage in pursuit of his fourth successive world title.
But Norris produced a superb drive on the hard tyres as he clawed away at Leclerc's advantage, getting within DRS range before Leclerc ran wide at the final corner to yield second place.
Sainz cruised to his second win of the season in a boost to Ferrari's constructors' championship hopes.
Mercedes pair George Russell and Lewis Hamilton duelled throughout, with Hamilton finally passing his team-mate with five laps remaining to claim fourth.
Perez pitted at the end from 16th and finished last in what could prove to be his final home race.
