What is Burnham’s path to becoming Labour leader and PM?

How could MPs who want Sir Keir Starmer to be replaced force a leadership contest and who could stand?

​What is Burnham’s path to becoming Labour leader and PM? How could MPs who want Sir Keir Starmer to be replaced force a leadership contest and who could stand? How could MPs who want Sir Keir Starmer to be replaced force a leadership contest and who could stand?