Tuesday briefing: What Trump’s triumph tells us about the state of the presidential race

Good morning. Last night, the race for the US presidency formally started – and Donald Trump has won the first round by a landslide. With 99% of votes counted, Trump has 51% of Republican support in the Iowa caucus – a victory of unprecedented dominance for any race not involving a sitting president.

Ron DeSantis got 21% of votes, a very distant second place that he tried to present as a success – while Nikki Haley finished a disappointing third with 19% but claimed she now had the momentum to challenge Trump. In truth, though, the result is so decisive that it’s all but impossible to see anyone but Trump taking the nomination from here.

Today’s newsletter, with the Guardian’s David Smith at the Trump victory party in Des Moines, explains what the results in Iowa mean for each of the three leading Republican campaigns. Here are the headlines.

Conservatives | Rishi Sunak is facing a Conservative meltdown over the Rwanda deportation bill after two deputy chairs said they would support rebel amendments aimed at blocking international human rights laws. Lee Anderson and Brendan Clarke-Smith have defied the prime minister by backing rightwing challenges to the bill, which will be debated by parliament on Tuesday.

Middle East crisis | The Houthi militia group has continued to attack commercial shipping, hitting an American-owned container ship with a ballistic missile in defiance of US and UK strikes on Yemen. While the strike caused no major damage, it will add to fears that the militia group retains the ability to threaten commercial shipping.

Rail strikes | Train drivers have called a further week of rolling strikes across England from late January in their long-running dispute with operators over pay. Members of the Aslef union