Labour’s Deputy Leader Tom Watson reportedly survived a trigger ballot on Tuesday night, which would have meant he would have faced a deselection challenge.
Mr Watson has enraged many supporters of Labour leader Jeremy Corbyn with his comments which were perceived as undermining him but he seems to have narrowly survived being replaced as the party’s candidate for West Bromwich East.
But Mr Watson is not alone in facing a challenge from the Left of his party and Boris Johnson is also keen on purging from the Conservative Party dozens of MPs who have either rebelled or threatened to rebel over Brexit.
So who faces the biggest threat?
Dominic Grieve (Conservative)
Remainers consider him a saint for his role in standing up to Boris Johnson, and Theresa May before him, on Brexit but many Tories consider Dominic Grieve the ultimate traitor.
Grieve, 63, has been Tory MP for Beaconsfield, an affluent constituency just outside London, since 1997.
He was Attorney General between 2010 an 2014 under David Cameron but was sacked when he spoke out in defence of the European Court of Human Rights.
Grieve is from the liberal wing of the Tory Party and his pro-European sentiments mean he is unlikely to be selected as the candidate for Beaconsfield.
Jason Behenna, the Deputy Chairman of the Beaconsfield Constituency Conservative Association, told The Sun: "He has failed two confidence votes already, and has to go before the Executive if he wants re-adoption as our candidate. He would do well to remember who he is representing and their expressed wishes."
Expect a huge queue of prospective Tory MPs lining up for the safe seat if it is declared vacant.
Virendra Sharma (Labour)
The MP for Southall in west London has one of the biggest majorities in the country - 22,090 - and his constituency, which is overwhelmingly South Asian, is a Labour stronghold.
But Sharma, 72, has fallen out with his Constituency Labour Party and earlier this year they passed a vote of no confidence in him because of his “poor attendance at CLP meetings” and also because he was accused of failing to take up cudgels on behalf of residents who are mired in a dispute with the Labour-controlled council over air pollution at a former gasworks site which is being redeveloped for housing.
Onkar Sahota, a member of the Greater London Assembly, is waiting in the wings if a trigger ballot is called, although he does not have particularly left-wing credentials.
Sir Nicholas Soames (Conservative)
Winston Churchill’s grandson, Sir Nicholas Soames, lost the party whip after voting against the government on no-deal Brexit and is likely to face an uphill battle for selection.
Sir Nicholas, 71, may well decide to retire with his dignity intact rather than facing a bruising and humiliating battle to be reselected.
If he does go there will be a queue of people wanting his safe seat in Mid-Sussex, where he has a 19,000 majority and has been MP since 1997.
Among them could be Amber Rudd, who quit as Work and Pensions Secretary at the weekend but voted with the government in the crucial Brexit votes.
Rudd, 56, has a wafer-thin majority of only 346 in Hastings and would almost certainly lose her seat to Labour’s Peter Chowney in a general election.
She has been tipped for a “chicken run” to Mid-Sussex before but in 2018, when asked whether he would vacate the seat for Rudd, his one-word response was “Balls”.
Diana Johnson (Labour)
The Labour MP for Hull North, Diana Johnson, was the first to be “triggered”, last week.
The trigger ballot means she will not be automatically reselected but will have to go into a battle with a number of other candidates from an all-women shortlist.
Johnson was defended by fellow moderate, Caroline Flint, who said she was a great MP.
Baroness Chakrabarti, Labour's frontbench chief legal adviser, told Sky News: “There will be a shortlist - it'll be an all women shortlist - and no doubt she'll be on it. I don't believe that this is targeted, from what I've heard, this is not some plot or some factional polarisation issue.”
Johnson, who has been MP since 2005, resigned from her job as a shadow minister in the wake of Hilary Benn’s “coup” against Jeremy Corbyn and she voted for Owen Smith in the leadership election, which is possibly the main reason she faces deselection.
Ed Vaizey (Conservative)
The Tory MP for Wantage in Oxfordshire, Ed Vaizey, is now independent after losing the whip after he voted against the government as one of the 21 rebels.
Vaizey was Culture Minister between 2010 and 2016 but fell out of favour with Theresa May and Boris Johnson.
Wantage and Didcot Conservative Association told the Oxford Mail: “The association officers would like thank Ed for all his hard work since his selection in November 2002 and his election in 2005. Three years since the biggest democratic vote in our nation’s history, we need to get on and deliver on that referendum result and move on as a party and a country. We will decide on the selection of a Conservative Parliamentary Candidate in due course.”
Vaizey, 51, may well decide to go back to his old career as a barrister rather than seek to win through the selection process.
The constituency has a 17,000 Tory majority so there will be no shortage of suitors.
Liz Kendall (Labour)
In 2015, after Ed Miliband stood down as leader of the Labour Party, Liz Kendall was one of the first to throw her hat in the ring.
But her Blairite bandwagon crashed off the road and she was heavily defeated by Jeremy Corbyn - who won almost 60 percent of the votes, compared to 4.5 percent for Kendall.
Ever since then Kendall has known her days in the party are numbered and the inevitable process to deselect began earlier this week.
Left-wingers within Leicester West Labour Party have started the trigger ballot process and hope to deselect her.
Ms Kendall, a Cambridge graduate, told the Leicester Mercury: “I will work day and night to convince Labour party members in Leicester West to re-select me as their candidate for the next election. I love being the Labour MP for Leicester West. Serving my constituents and this city is the greatest honour of my life."