Charmant's 23-length win, at odds of 16-1, in the Follow At RacingTV On Twitter Handicap Chase took Hughes to 115 for the season.
Johnson, champion in each of the last four years, is on the sidelines after breaking his arm in a fall at Exeter on Tuesday - and Hughes' other nearest challenger Sam Twiston-Davies trails by 29.
Hughes nonetheless said: "This is by no means an open goal. I have to stay in one piece - and Richard Johnson will be back. As he's shown in other years, he's a determined man."
Should Hughes prevail at the end of April, he will become the first northern-based winner of the title since Jonjo O'Neill in 1979-80. He is wary of the pitfalls of jump racing, however.
"What happened to Richard Johnson proves what a jump jockey lives with day to day - you're only one fall away from your season being over," he said.
"One minute you're up, the next you're down. Don't get me wrong - I'd absolutely love it (to win the title). But it's by no means a foregone conclusion. You try not to put it at the forefront of your mind - something that then clouds your judgement."
He admitted, after James Ewart's Charmant was left clear by The Paddy Pie's unlucky fall at the third-last, that his judgement was momentarily awry at the next fence, where his partner made the necessary adjustment.
"That was jockey error - I went and squeezed him for something that wasn't there," he said. "Luckily he's cleverer than me! I left him alone at the last."
Tavus had earlier kept himself on course for a possible trip to the Cheltenham Festival as he returned to winning form in the Every Race Live On Racing TV Juvenile Hurdle.
Jedd O'Keeffe's youngster could not handle Triumph Hurdle hope Allmankind when sixth of eight in the Grade One Finale at Chepstow last time.
But after Hughes and market rival Dark Lochnagar took an early fall, Tavus made no mistake under Joe Colliver for a three-length success at 2-1, his second win in three over jumps.
Asked if a trip to Cheltenham in March beckons for the Boodles Juvenile Handicap Hurdle, O'Keeffe said: "I'm sure he'll have an entry."
The North Yorkshire trainer hopes a move back up in class may suit Tavus, a three-time winner on the Flat for Roger Charlton.
"I'd like his jumping to tidy up," he added. "The race has obviously fallen apart a little bit, but I think he would be a horse that would be better tracking pace and produced a little bit later - but Joe's had to do what he's had to do today.
"I think he might jump a bit slicker in a better race - but he's going to need to, isn't he?"
