The final two candidates in the race to be the next leader of Britain's Conservative Party, and almost certainly the country's next prime minister, will be decided on Thursday.

Jeremy Hunt, the foreign secretary, Michael Gove, the environment secretary, and Sajid Javid, the home secretary, will battle to be the challenger to former London mayor Boris Johnson in two rounds of voting after the outsider in the race, International Development Secretary Rory Stewart, was eliminated.

Stewart's surprise run to the third round was brought to an end on Wednesday, as Johnson further cemented his place at the head of the pack by winning the support of 143 of the 313 Conservative MPs.

Johnson supporters reportedly lent their support to Javid as part of a tactical voting plan to eliminate Stewart, a centrist and strong critic of the former foreign secretary, having taken a similar approach to knocking out Brexit hardliner Dominic Raab on Tuesday.

Stewart, whose unconventional #RoryWalks social media campaign propelled him into the national spotlight, conceded after his loss that his support had been among “people in the country” rather than the Conservative Party.

Hunt (54 votes), Gove (51) and Javid (38) remain closely matched going into the last rounds of voting, and each must now convince their fellow MPs that they are the strongest challenger to Johnson among the 160,000 Conservative members who will make deciding votes.

All the remaining candidates have said they would be willing to take Britain out of the European Union without a deal if new terms cannot be reached with the bloc, though Javid has taken a harder line in recent days by guaranteeing Brexit would take place by October 31.

Johnson, whose supporters include hardline Brexiteers and no-deal opponents, appeared to equivocate on the issue in a rare media appearance on Tuesday. However, that didn't stop him winning the support of eliminated candidate Raab ahead of the third round vote.

The frontrunner, known for gaffes and incendiary comments, has kept media exposure to a minimum so far in the race. His campaign is being overseen by Gavin Williamson, who was sacked as defense secretary by departing Prime Minister Theresa May over alleged leaks of classified material. He previously maintained party discipline as chief whip.

Stewart is yet to endorse any of the remaining contenders, but admitted holding talks with Gove over a joint ticket. If Gove can take the majority of the eliminated candidate's supporters, he will be in a strong position to leapfrog Hunt into second place and take on Johnson.

That would set up a contest with an intriguing subplot between the co-leaders of the Vote Leave campaign in the 2016 Brexit referendum.

Gove was Johnson's campaign manager in the leadership contest that followed David Cameron's resignation, but torpedoed the then frontrunner's bid on the day of its launch by making his own failed attempt to take the top job.