Divisions over Europe have ultimately cost the job every British Conservative prime minister since Margaret Thatcher.
Theresa May confidence vote on Wednesday would at best mean she lives to fight another day. The great dividing line in the most successful political party in the Western world cannot be healed so readily.
While Mrs May has repeatedly promised that she will be the prime minister to deliver the UK exit from Europe on March 29, 2019, the challenge she faces has welled up from the ranks of the most hardline supporters of Brexit.
Since she assumed the leadership in 2016, Mrs May has been dogged by her remain stance in the referendum that June. Brexiters don’t believe she will deliver at the ultimate hour.
David Cameron resigned after the referendum was lost in 2016. He had promised to call the vote as a political tactic to squeeze support for the United Kingdom Independence Party ahead of the 2015 election.
It was a very successful gambit but once he had a majority in the House of Commons, he was honour bound to call the vote that blew up his leadership. Mr Cameron on Wednesday tweeted that Mrs May had his full support.
John Major, the prime minister for six and a half years in 1990s, fought a series of showdowns against the eurosceptics who opposed the European currency, the euro, and the creation of the EU. At one point he called a leadership vote against himself to lance the pressure. He won but the turmoil continued.
It was all too much for the electorate who handed a landslide victory to Tony Blair in the 1997 election.
While Mrs Thatcher was a champion of the EU single market, her antipathy to Brussels as it tried to launch the euro and forge “ever closer union” at the political level at the end of the Cold War hastened her demise.
Senior cabinet ministers rebelled against the long-serving leader. Under the rules at the time, prime ministers had to win a confidence vote by a clear margin. However, on a visit to Paris Mrs Thatcher fell four votes short of an outright first round victory. Defiant, she declared: “I fight on, I fight to win”.
Within days she was gone.
The Conservative chose leaders via a so-called magic circle until the mid-1960s. The senior figures, known as the men in grey suits, would visit an outgoing leader to deliver the message his time was up.
The introduction of leadership ballots has since seen Conservative prime ministers and opposition leaders ousted as soon as the inevitability of election defeat becomes painfully obvious.
That is the reality that has hung over Mrs May for almost all of her premiership.