The Philippines' dominant Marcos and Duterte political dynasties, uneasy allies for two years, are gearing up for an election showdown that could upset policy stability in the Southeast Asian nation in the coming years.

Vice President Sara Duterte's resignation as education minister in President Ferdinand Marcos Jr.'s Cabinet was followed on Tuesday by her bombshell announcement that her father, ex-President Rodrigo Duterte, and two brothers would run for the Senate next year.

The collapse of the alliance had long been expected, but the political challenges by the Duterte men could upset Marcos' hopes of consolidating power so he can groom a potential successor for 2028, when analysts say Sara Duterte may seek the top job. Philippine presidents are limited to a single six-year term.