Sailor Ben Ainslie powered to the top of the Finn standings with a fourth and a first place on day three in Athens.
Ainslie, who was 19th overall after a disqualification in race two, became the third Team GB member to lead in his class on the Saronic Gulf.
Shirley Robertson and her crew head the Yngling keelboat class and Nick Rogers and Joe Glanfield lead the 470 event.
Ainslie may see his disqualification overruled - the jury are deciding whether to reopen the case.
The gold medal hopeful leads the discipline after six of 11 races with 16 points, one clear of Spain's Rafael Trujillo with former leader Mateusz Kusznierewicz third on 25.
"I am pretty tired after today to be honest but I am relieved that I have been able to pull things around and get myself back in with a chance," said Ainslie.
Ainslie's campaign looked to be virtually over when France's Guillaume Florent successfully protested that he had contravened right-of-way rules in race two on Saturday.
Team GB secured video footage from television cameras which Ainslie believed
proved his innocence, but on Monday Olympic officials deemed the appeal came too late.
The jury can, however, decide to reopen the protest if they consider it appropriate and will review the video overnight.
Ainslie, the three-time world Finn champion, recovered from the setback with two firsts on Sunday, while a fourth in race five put him third on Monday before he won the sixth race to take top spot.
Robertson's Yngling crew lead the standings after six races
His biggest threat for gold, Poland's Kusznierewicz, was 11th in race five and disqualified in race six for crossing the start line too early.
"Certainly things are looking good so far but there's a long way to go yet," said British sailing boss Stephen Park.
"The team have all rallied around Ben and no-one doubted that if anyone could come back it would be him. It shows what a great sailor he is. He's got incredible focus.
"But he's working on the basis that he's disqualified and is head down and doing his best."
Robertson, and crew Sarah Ayton and Sarah Webb, finished fourth in race five and third in race six on Monday to stretch their lead to nine points over the Danish trio.
The Finn and the Yngling were the only classes to compete on Monday after organisers deemed the local Meltemi winds too strong for the other divisions.
Rogers and Glanfield lead Americans Paul Foerster and Kevin Burnham by eight points overall after four races.
Meanwhile, the men's Mistral windsurfer class will re-sail their opening race after the jury upheld a protest from three of the fleet that race organisers should have abandoned Sunday's race over a
The men's Star double-handed keelboat, men's double-handed 49er dinghy and men's Tornado catamaran classes have all yet to start their Olympic regatta.
Sailors in all classes except the 49er are allowed to discard one score after five of their 11 races. The 49ers discard two in total from 16.