A concerted email campaign by England fans could rob Ronaldo of the World Cup's best young player award.
Ronaldo has been linked with Real Madrid
The Portuguese winger, pilloried for his part in the sending off of Wayne Rooney, was leading the Fifa website vote by a huge margin.
But an email urging fans to vote for Ecuador's Luis Valencia instead led to an incredible 24-hour turnaround.
Ronaldo went from 210,290 to 241,775 votes, but Valencia soared from 195,377 to 331,087. Fifa has the final say.
As well as Ronaldo and Valencia, the other player nominated by fans is Argentina's Lionel Messi.
The other three candidates, chosen by Fifa's technical study group, are Germany's Lukas Podolski, Switzerland's Tranquilo Barnetta and Spain's Cesc Fabregas.
The original email sent to fans read: "There is a very real danger that Cristiano Ronaldo will be voted the fans' best young player at the World Cup despite his pouting, diving, pretty boy antics - designed mainly to get himself a lucrative transfer to Real Madrid.
"He is currently first in the Fifa voting, ahead of Luis Valencia of Ecuador. Do the decent thing by voting for Valencia.
"It doesn't matter who you support or if you haven't seen them play, just stop Ronaldo. Send this on to any caring conscientious true football lover."
The winner of the award will be announced on Friday, when a shortlist of six players - three chosen by the public and three by Fifa - will be whittled down to one by a 14-man panel.
If they go with the popular vote it will cap a miserable few days for Ronaldo, who left the field in tears after Portugal's defeat by France in the World Cup semi-final.
He was roundly booed every time he touched the ball, with a sizeable contingent of England fans in the crowd leading the way.
Rooney was sent off against Portugal
The hate campaign started after the quarter-final between England and Portugal in Gelsenkirchen, when Ronaldo was pushed by Manchester United team-mate Rooney, just before the England striker received a red card.
Ronaldo was caught on camera apparently winking at the bench after Rooney's dismissal, infuriating England fans.
In a final twist to the email saga, the Daily Record reported that it was in fact Scotland fans who had helped propel Ronaldo to the number one spot with a viral campaign of their own designed to heap further misery on England fans.
The paper said: "Tartan Army internet message boards have been urging fans to pluck for Ronaldo on the official World Cup website - and so far things are working a treat."