power base (of a government)
Refers to the foundation of support that sustains a government or administration, including political backing, public approval, and institutional strength.
The ruling party is trying to strengthen its power base by reinforcing local organizations.
The decline in approval ratings is shaking the government's power base.
支持基盤 is a broader term for a support base, often used for individuals or organizations, while 政権基盤 specifically refers to the foundation of a government's power.
Compound of 政権 (political power) and 基盤 (foundation, base).