Power is a tool for managers to influence their organizations and a vital resource to stay in charge. While having a general understanding of CEOs’ inclination to increase their power, we know little about why and how they work on their power base. We adopt a political capital perspective on power and develop a model on a CEO’s portfolio of political capital. We suggest that managers optimize their portfolio structure and diversify between different power sources. We predict that CEOs convert episodic, short-term available forms of political capital into more enduring forms to increase the durability of their portfolio. The analysis of a hand-collected sample of 245 German firms from 2010 to 2018 supports our prediction that CEOs exploit succession events and favorable shareholder voting for big bath accounting. Big bath accounting provides a highly durable form of economic capital as it brings earnings reserves under the control of the CEO, who can flexibly boost firm profits. Our study contributes a portfolio model of CEO power integrating accumulation and diversification aspects of political capital. We document how managers convert between different forms of political capital, increase their portfolio’s durability, and store their power. In the German two-tier board system, we leverage separate discharge voting results for managers and non-executive directors and reveal that merely symbolic governance mechanisms provide a substantial and dynamic source of power on the board.