Labour's new leader will romp to victory on April 4, the same day as the Grand National.
The contest officially starts tomorrow.
Five MPs have so far declared they want the top job – Shadow Brexit Secretary Sir Keir Starmer, Shadow Foreign Secretary Emily Thornberry, Shadow Treasury Minister Clive Lewis, former Shadow Energy Secretary Lisa Nandy and outspoken backbencher Jess Phillips.
Party chairman Ian Lavery is also expected to run.
Labour says the postal ballot of members will run from February 21 to April 2.
Candidates need to secure the nominations of least 10% (22) of the party’s MPs and MEPs.
The freeze date for new members to join and be eligible to vote in the postal ballot will be January 20.
As in 2016, people can also pay £25 to join as a registered supporter.
Meanwhile, another candidate today enters the race for the deputy leadership, triggered by Tom Watson standing down.
Writing exclusively for Mirror.co.uk, Labour’s only Scottish MP Ian Murray says the party must become a “credible alternative government of the future”.
He adds: “Voters don’t want politicians to agree with them all the time – they want us to have the debate and try to convince them.
“On the major constitutional issues of our time – Scottish independence and Brexit – we must be clear with people where we stand.”
His rival Angela Rayner told a crowd in her home town of Stockport, Gtr Manchester today: “We must rethink and renew our purpose, and how we convince the people to share it.”
Candidates must win the support of 10% of MPs and either 5% of constituency parties or 5% of affiliates (trade unions, socialist and co-operative parties) to get on the ballot paper.
They then face a vote by Labour's 500,000-odd members.
