Carrie Ford's mount Forest Gunner could start as favourite for the John Smith's Grand National at Aintree on Saturday.
The 33-year-old mother, who has come out of retirement for the big race, is bidding to become the first woman to ride a National winner.
And the major bookmakers have cut the horse's price after sustained backing from punters in recent days.
The support comes despite four-time National winning trainer Ginger McCain dismissing a lady rider's chances.
Forest Gunner, who is trained by Ford's husband Richard, is now just an 11-1 chance with Ladbrokes, William Hill and Coral.
Irish challenger Hedgehunter, a faller at the last when in contention last year, and the 2004 runner-up Clan Royal are shorter prices.
But the row over McCain's comments and the prospect of history in the making is guaranteed to earn Ford widespread media coverage this week.
McCain, who saddled Red Rum to three wins in the 1970s and triumphed again with Amberleigh House last year, claimed that "women don't win Grand Nationals".
Coral spokesman David Stevens said: "Unlike Ginger, plenty of punters think a lady rider can win the National and are backing this horse accordingly.
"Forest Gunner could well go off favourite if the money continues to pour in."
The 11-year-old horse, who won the 2004 Fox Hunters' Chase over one circuit of the National fences, is the second-biggest loser in Ladbrokes' ante-post betting book, with £330,000 potential losses on the gelding.
Only Amberleigh House, would cost the firm - Britain's biggest bookie - more if he won.
Ford will be the first woman since Rosemary Henderson, who came fifth in 1994, to line up for the Aintree showpiece.
And despite the fact that only two women have completed the race in the past, Hills make her an odds-on shot at 5-6 to get round.
There could be a 'Girl Power' theme for the Aintree marathon, with trainer Lucinda Russell predicting a good run from her contender Strong Resolve.
Our man Cornelius Lysaght told of three potential Aintree winners back in February:
Amberleigh House -
Then: 20-1 Now: 9-1
Forest Gunner -
Then: 25-1 Now: 11-1
Strong Resolve -
Then: 25-1 Now: 16-1
The nine-year-old, currently priced at about 16-1, still needs a few horses to come out of the race to be guaranteed a run.
But he was an eye-catching second to Silver Birch in the Welsh National last December, and the forecast rain on Merseyside may be a bonus.
"I think he will run a good race and I think conditions will suit him," said Russell.
"He coped with heavy ground better than the other horses last time but ideally he wants it good to soft or soft."
Peter Buchanan, who rode Forest Gunner when he won at Haydock in February, will be aboard Strong Resolve at Aintree.
One horse who will definitely miss out is the Philip Hobbs-trained Gunther McBride.
"He's just a little bit lame and I think it would be pushing him," said the trainer's wife Sarah.
Hobbs' Somerset stable will be represented by Double Honour, who was runner-up to Forest Gunner in the Red Square Vodka Gold Cup at Haydock last time.