Public criticism has mainly come from those ousted from government in the reshuffle. Europe’s biggest economy has long been one of its most stable democracies, with no history of rattling through leaders like postwar Italy or post-Brexit Britain. But the expected success of the AfD, in elections in which the CDU is expected to lose ground, is upending the country’s conventional political dynamics. The AfD — now the most popular party in national polls — would seek to capitalize on further coalition unrest. Replacing a chancellor years before the end of his term would mean venturing into largely uncharted political territory.