Wiktionary
political vacuum
n. a state of relative anarchy compared to neighboring states, often caused by death of the head of state before a successor could be designated
Usage examples of "political vacuum".
The NASA hierarchy was still a political vacuum, and Deke set about filling it….
Your brother's removal leaves a deadly political vacuum in the region.
Kathandrion had been wise enough not to raise his heir in a political vacuum, and the Mimbrate emmissary to the court at Vo Wacune had given Alleran instruction in the somewhat overly-involved courtesies of the Mimbrates.