Rebecca Long-Bailey is 6.411/2 on the Betfair Exchange to be the next Labour leader after the Unite union endorsed her to succeed Jeremy Corbyn.
Unite's general secretary Len McCluskey said Long-Bailey was "brilliant, brave and courageous" and "best placed (of the Labour leadership candidates) to take the fight to the Tory party."
She is 24.023/1 to Britain's next Prime Minister and faces a huge task to win the Labour leadership with bettors making Keir Starmer a shoo-in for the job.
Three candidates likely to make members' ballot
Unite's endorsement came a week after Momentum, the grassroots movement that supported Jeremy Corbyn's leadership of Labour, announced its support for Long-Bailey.
To make the Labour members' ballot, leadership candidates need to secure the support of three unions and affiliate groups representing 5% of the membership, or 33 local branches, by 14 February.
Frontrunner Starmer 1.364/11 and Lisa Nandy 9.617/2 have secured this level of support and Long-Bailey now needs the backing of just one more union or affiliate to confirm her place on the members' ballot.
Unions divided over leadership hopefuls
Unite's support for Long-Bailey is no surprise but it is significant as the union is Labour's largest affiliate and was the party's biggest financial backer during last month's general election.
Of the UK's big three trade unions, Starmer has the support of Unison, while the GMB are backing Nandy, so that's one each for the three candidates who are set to make the ballot. Members can vote from 21 February.
Jess Phillips dropped out of the contest this week while the other remaining candidate, Emily Thornberry 90.089/1, is unlikely to go through to the next stage of the contest.
In 2010 and '15, the winners - Ed Miliband and Corbyn respectively - had the support of both Unison and Unite, although the GMB made the ill-fated decision to back forgotten-man Owen Smith in the leadership contest of 2016.
Unite is the only one of the big three that isn't supporting Angela Rayner's 1.041/25 bid for the deputy leadership and have instead opted to support her nearest rival in the betting Richard Burgon 10.09/1.
Whoever is the next Labour leader will have won the contest without the support of two of the big three - Unite, Unison, the GMB - and it will be interesting to see what this means in terms of their much heralded quest to reunite the party following the years of division under Corbyn.
In the meantime, thousands of new members joining Labour are believed to be good news for Starmer. Newsnight reports that it spoke to constituency Labour parties across the country where there had been an average 20% increase in membership since the general election on 12 December.
Much was made of the role entryism played in Corbyn's victory in 2015, with thousands of people joining to vote for a candidate who would return to the party to its left-wing root. Now it is believed that new Labour members are joining for the opposite reason - to vote for Starmer and deny Long-Bailey who is seen by many as the left-wing continuity candidate.
Varadkar in fight of his political life
With less than two weeks to go until Ireland's general election the betting indicates that the outcome is on a knife-edge. Leo Varadkar, who has been the country's prime minister since 2017, is 4.216/5 to be returned to power with Micheal Martin 1.141/7 to assume office after the election.
Polling today shows Martin's Fianna Fail (26) leading Varadkar's Fine Gael (23) by three points and bettors make the former 1.21/5 to win most seats. Neither party has the support necessary to form a government on their own and will almost certainly need to go into coalition after the election.
For people in the UK, its' easy to underestimate the disgruntlement that many Irish voters feel with their government precisely because Varadkar has been praised across the country's political spectrum for his handling of Brexit. Polling shows, however, that many voters are unhappy with Fine Gael'a policies on housing and health and it is these domestic issues which have dominated the election campaign so far.
For the next fortnight, Varadkar will be in the fight of his political life.