The Cup is the missing link in Williams quest for the 'Grand Slam' consisting of Tuesday's race, the Caulfield Cup, the Cox Plate and Golden Slipper.
Williams was close to winning the three major Melbourne races in 2011 after claiming the Caulfield Cup on Dunaden and Cox Plate on Pinker Pinker.
He failed in his bid to have a suspension overturned with the winning ride on Dunaden going to Japanese-based Frenchman Christophe Lemaire.
Williams is bullish about Vow And Declare's hopes on Tuesday.
"I wouldn't say he's my best chance," Williams said.
"Dunaden was my best chance but I was suspended and I've had nice horses before and since.
"But he's a great chance and I'm looking forward to it."
Williams will be having his 16th Cup ride with his best result third on Mount Athos in 2013.
Vow And Declare has drawn barrier 21 on Tuesday and after studying the form Williams is buoyed by the fact it looks an open race.
After partnering Vow And Declare early in his career, Williams was back aboard the Danny O'Brien -trained gelding in the Caulfield Cup (2400m) on October 19.
Vow And Declare's second to Mer De Glace gave Williams the confidence Vow And Declare will run out the 3200m on Tuesday.
"I've done all the form and I'm happy," Williams said.
"I'm happy with the horse and we've just got to see how these international horses compete for the first time.
"I worked him at Flemington last week, the only time I've been on him since the Caulfield Cup, and he was good.
"I'm the race jockey. Danny knows what he's doing, and I'll stick to what I do."
CRAIG WILLIAMS CUP RECORD:
2000 Citra's Prince 12th
2001 Mr Prudent 11th
2002 Requiem 22nd
2005 Kamsky 16th
2006 Mandela 9th
2007 Scenic Shot 16th
2008 Varavees 14th
2009 Leica Ding 14th
2010 Monaco Consul 14th
2012 Dunaden 12th
2013 Mount Athos 3rd
2015 Hokko Brave 17th
2016 Qewy 4th
2017 Wall Of Fire 20th
2018 Youngstar 6th