Longman Dictionary of Contemporary English
power base
noun
EXAMPLES FROM OTHER ENTRIES
▪ McClardy's power base is among working-class Catholics.
EXAMPLES FROM CORPUS
▪ But middle-class flight destroys a school system because when middle-class parents flee, so does the power base.
▪ Politicians who have their power base in these areas, including several presidential candidates, are also implicated.
▪ Providing information that reduces uncertainty is a second way a department can increase its power base.
▪ The Conservatives suffered the biggest reversal of fortunes, losing two seats in their North Down power base.
Wiktionary
power base
n. The source of a person's or organization's power or influence
Usage examples of "power base".
During the last five years he had steadily increased his support amongst the warring tribes of the high country, and solidified his power base among the Britons of the south.
A foot in both camps, but with an eye to your own power base, as always.
Any act of kindness I performed had come out of my need to enhance my power base.
At the same time, she doesn't want to give up her power base in North Dade and Miami Beach.
Because he doesn't have a real power base of his own, he's desperate to prevent open class warfare from breaking out.