A surprisingly disciplined campaign risks derailment as Trump lashes out at his former UN ambassador for staying in race

It was a moment for Donald Trump to be gracious, magnanimous, perhaps even presidential. Instead he lashed out at his opponent’s clothes. “When I watched her in the fancy dress that probably wasn’t so fancy, I said, ‘What’s she doing? We won,’” he said of rival Nikki Haley in New Hampshire on Tuesday night.

Trump had just won the first primary election of 2024 and all but clinched the Republican nomination for US president. Party leaders and campaign surrogates are now eager to banish Haley to irrelevance, move on from the primary and unify against Democrats. They want Trump to pivot to an almost inevitable rematch with Democrat Joe Biden in November.

Yet the 77-year-old remains consumed with rage over Haley’s unwillingness to quit the race. His petulance offers a reminder of the unhinged behaviour that turned off independent voters in New Hampshire and could prove to be a liability in a head-to-head contest with Biden. It is also at odds with what is an unusually professional and disciplined campaign operation.

Wendy Schiller, a political scientist at Brown University in Providence, Rhode Island, said: “Donald Trump wants the race to be over and we see evidence of why that’s important for the Trump campaign from his speech, which was essentially a train wreck and exhibited all the worst tendencies of Donald Trump. It was an undisciplined Trump and this is what turns off independent voters.”