Fighting to keep hold of her job, Theresa May uttered the words she will come to gravely regret in 2019

Regrets? Theresa May will have more than a few after a turbulent year. She won’t share them with us, of course. She will start the new year “getting on with the job”, and to prove it, she has summoned cabinet ministers to a special meeting about Brexit next Wednesday.

In 2019, the prime minister will come to regret words she uttered in the heat of battle in 2018: “In my heart I would love to be able to lead the Conservative Party into the next general election. But I think it is right that the party feels that it would prefer to go into that election with a new leader.”

The pledge was made to a private meeting of Tory MPs an hour before a vote of confidence in her as party leader. Even after it, more than a third of Tory MPs (117) voted against her. Without it, her premiership might have come to an end. Classic May – survive, but live to die another day.

Afterwards, May took some comfort from the Tory rule under which she cannot face another party confidence vote for 12 months. But it might prove cold comfort. Her allies hope she can stay in Downing Street for more than two years. But I think they will be disappointed.

May was deliberately unspecific about her departure date. Her comments related to the next scheduled election in 2022. So she did not rule out leading her party into a 2019 election triggered by Brexit – a slim possibility in my view, but one that does exist. After her disastrous campaign at last year’s election, many Tories would be horrified, but there might not be time to remove her.

By conceding she will depart before 2022, May has shortened her own shelf life. When Tony Blair was agonising over when to step down, his former policy head Andrew Adonis rightly told him in a memo: “Once you ‘name the date’, your authority will drain away rapidly and will be followed by growing calls for you to bring the date forward to ‘end the lame duckery’ …There are no ‘dignified exits’ and ‘orderly transitions’ – just exits and transitions, all more or less ragged and unsatisfactory.”

Both Blair and David Cameron provoked a wave of speculation by putting a time limit on their premiership. May starts from a lower base; her authority is already weak. She will find that her cabinet ministers treat her differently now. Discipline in the cabinet, already cracked by the Brexit pressure cooker, will be even harder to enforce. This could deepen her problems if, as expected, her Brexit deal is rejected by the Commons next month.

At least seven cabinet ministers want to succeed May, so that is bound to influence their actions. It is no coincidence that the two front-runners, Sajid Javid and Jeremy Hunt, enjoyed the highest media profile in a very quiet Christmas week. The home secretary made headlines by telling BBC Radio 4 that there could be “cultural reasons” for men with a Pakistani background becoming involved in grooming gangs. The foreign secretary chose The Daily Telegraph, the paper read by many of the 120,000 Tory members who will choose the party’s next leader, to announce that the UK will do more to protect Christians being persecuted in the Middle East. Both Javid and Hunt are interested in a “managed no-deal” if May’s agreement is sunk, knowing such talk plays well with Eurosceptic MPs and party members.

May’s allies are irritated by the jostling for position, but she has made the problem bigger by acknowledging her own time in No 10 is limited. Even if she somehow gets Brexit over the line in March, Tory backbenchers tell me they will move quickly to persuade her to stand down, to allow her successor to be in place by the Conservative annual conference in October. Although the 12-month rule protects her until next December, it could easily be overtaken by events.

If hardline Eurosceptics cannot block a version of May’s deal, they will focus on a new target: negotiations on a long-term UK-EU trade deal. Some believe the political declaration on the future relationship is so vague that, with one of their own in place as leader, they can yet win a limited Canada-style free trade deal.

In her speech to this year’s Tory conference, May pleaded for time to implement her stalled domestic agenda once the tortuous Brexit process ends. But by accepting she will not be at the helm for the next scheduled election, she has made it easier for her many internal critics to argue that the post-Brexit programme should be a task for her successor. That agenda will be heavily shaped by the government-wide spending review next year – another reason for her to depart sooner rather than later, in the eyes of Tory MPs.

If May again defies the odds, delivers Brexit and tries to “get on with the job”, the response from her ungrateful party will probably be “thanks, but no thanks”.