A decision to bomb Iran would be a war of choice. If Mr Trump scores what looks like an easy victory, without ground forces, he is likely to be hailed as a forceful leader. If he lands the country in a regional quagmire and the price of oil soars, the public verdict will probably be harsh. ■

The prospect of a U.S. strike against Iran has exposed divisions among Trump supporters, with part of the rift on full display when Tucker Carlson, on his streaming program, clashed with Republican Senator Ted Cruz.

Trump said he was waiting to see “whether or not people come to their senses.”