The contest to become Ireland’s next prime minister is turning into a one-horse race after the higher education minister, Simon Harris, secured the backing of nearly half his parliamentary party before he had even confirmed he was running. Within hours of nominations opening on Thursday to succeed Leo Varadkar, whose unexpected resignation as Fine Gael leader and taoiseach shocked the country, Harris had been endorsed by 24 of the party’s 54 TDs (MPs), senators and MEPs. Further clearing the path to his election, four high-profile potential rivals all ruled themselves out of the race on Thursday, leaving Harris – who would become Ireland’s youngest ever taoiseach if elected – the overwhelming favourite. Harris, 37, who dropped out of college to enter politics and became a TD at the age of 24, confirmed late on Thursday that he was a candidate. “I am declaring. I’m in and I intend to give this my all,” he told the public broadcaster RTÉ. “Whether there is a contest or not, I will be approaching this with vigour and energy. I will be listening to members across the country.” The enterprise minister, Simon Coveney, the justice minister, Helen McEntee, the public expenditure minister, Paschal Donohoe, and the social protection minister, Heather Humphreys, all said they would not run, with some also backing Harris. While nominations for the Fine Gael leadership do not close until lunchtime on Monday, it is possible the Wicklow TD Harris will not even face a challenger. One parliamentarian told the Irish Times the momentum behind him was “like a juggernaut”. Since the party’s rules stipulate that in leadership elections the votes of TDs, senators and MEPs count for 65% of the total, any rival to emerge before the deadline would need almost 100% support from councillors and grassroots members to overtake him. Paul Cunningham, of RTÉ, said: “I think it’s over. There is the capacity for contenders to come forward until Monday, but with Donohoe out of the race, it’s hard to see how anyone is going to stand against Harris.” The race was looking like “a coronation rather than a contest”, he said. Varadkar, who said he stepped down for “personal and political” reasons wants his successor as party leader chosen before the party’s annual conference on 6 April. Parliament is then expected to vote on that person succeeding him as taoiseach on 10 April. Speaking at an EU summit in Brussels on Thursday, Varadkar said he would follow party tradition by not endorsing any one candidate to succeed him since that would “allow me to support wholeheartedly whoever is elected as the next leader”. He said he had been thinking of quitting since Christmas and insisted “no event, no one thing” had pushed him into the decision, rather a feeling that it was time for someone who may have new ideas to take the party into the next election. “I made the final decision at the weekend, and I think once the decision was made in my mind it was important to act on it,” he said. Hinting at exhaustion, he said his partner, Matt, was delighted with his decision. He also took issue with those complaining about the timing of his departure months out from a general election. “There needs to be turnover politics,” Varadkar said. “Turnover is normal and not bad.” He laughed at suggestions he could be after a big EU job, saying he would remain as a TD in his Dublin constituency and campaign for his party’s local and European parliament election candidates but had not decided whether he would stand again. In March, Varadkar’s government suffered damaging defeats in two referendums on references to family and women in the constitution, but he insisted that the disastrous results “didn’t really” influence his final decision. Harris, who has held a number of ministerial portfolios including health and was widely praised for how he handled his brief during the Covid pandemic, was first elected to the Dáil, or parliament, in 2011, becoming the youngest TD at the time. He studied journalism, but did not complete the course. He is regarded by many of his colleagues as highly accessible and a good communicator who played a leading role during the referendum in 2018 that saw Ireland legalise abortion. Harris, who also served as a junior minister in the finance department from 2014 to 2016, would surpass Varadkar – who was 38 when he was first appointed in 2017 – as the country’s youngest ever prime minister if elected. Until Varadkar’s decision to quit it had been assumed Ireland would go to the polls to elect a new government in October. But Fine Gael’s coalition partners, Fianna Fáil and the Greens, have both said the administration should run its full term. Whoever wins will have up to 12 months before the next general election to try to overturn a wide opinion poll deficit: both Fine Gael and Fianna Fáil are trailing the main opposition Sinn Féin party. Opposition parties have demanded a snap election. Mary Lou McDonald, the leader of Sinn Féin, said: “Rather than limping on, rather than passing the office of taoiseach amongst yourselves again, the correct democratic route at this point is to go to the people.”