Wiktionary
prime ministership
n. The office of a premier or prime minister.
Usage examples of "prime ministership".
Thus, in politics, for example, we find that the British prime ministership has been turning over since 1922 at a rate some 13 percent faster than in the base period 1721-1922.
They had arranged his own accession to the Prime Ministership, he knew now….
But he'd insisted upon democratic Palestinian elections as part of his agreement to accept the prime ministership, and the PLC had readily agreed, so that wasn't likely to be a problem.
Not that the Prime Ministership hadn't made a dandy retirement from the Regency, and he was showing no signs yet of stepping down from that.