Former German Chancellor Angela Merkel has issued rare public criticism of her successor as the country’s center-right leader, the front-runner in Germany’s election next month, for putting to parliament proposals for tough new migration rules that only passed with the help of a far-right party.

Friedrich Merz’s hard-line shift on migration is a calculated gambit by the German conservative leader to neutralize the far right and deliver a breakthrough with wavering voters, according to people familiar with his thinking.