Sunak is the bookies' favourite to become the next prime minister, having lost out to Truss at the last leadership election just months ago.
He lost by a margin of 21,000 votes, with many members opposing him over his prominent role in toppling Boris Johnson.
But his accurate economic forecasts that his opponent’s widespread tax cuts were “fantasy economics”, makes his bid even more appealing to Tory MPs who have criticised 'Trussonomics'.
The former chancellor is the odds-on favourite with Paddy Power (4/5) to be the UK’s third prime minister of the year.
Penny Mordaunt, current leader of the House, is another favourite to lead the Conservative Party (7/4) and Defence secretary Ben Wallace (17/2), who was already a favourite last time but refused to run.
A shock return to Downing Street for former PM Boris Johnson is also priced at 14/1.
Read more: Pound up after Liz Truss quits as PM
Kemi Badenoch (20/1) is the fifth favourite. She's currently Secretary of State for International Trade and many Tories have claimed she could be the "last hope" for the party.
Separately the Guardian's political editor reported former minister Michael Gove was "ruled out" for the leadership. Current chancellor Jeremy Hunt has also ruled himself out of the race.
“Rishi Sunak may be the favourite to replace Liz Truss, but at 500/1, there’s great value on backing the lettuce instead. After all, it’s already lasted longer than the outgoing PM, so it looks like it has the political staying power that the Tories so desperately need.
“But, with Brexit still a huge sticking point for leadership hopefuls, the big question is: is the lettuce leaf or romaine?”
NEXT CONSERVATIVE LEADER
4/5 Rishi Sunak
7/4 Penny Mordaunt
17/2 Ben Wallace
14/1 Boris Johnson
20/1 Kemi Badenoch
33/1 Suella Braverman
40/1 Sajid Javid
40/1 Jeremy Hunt
40/1 Simon Clarke
66/1 Dominic Raab
500/1 The Lettuce
500/1 Neil Warnock
500/1 Roy Keane
500/1 Gary Neville