Jeffrey Pfeffer does a good job decomposing what it takes to attain power in the corporate world. If you think it takes intelligence or even high performance, you're working too hard.
According to his book, Power: Why Some People Have It And Others Don't, Pfeffer came up with seven personal qualities that help to build power: ambition, energy, focus, self-knowledge, confidence, empathy with others, and capacity to tolerate conflict. Intelligence and high performance didn't make the cut.
Pfeffer's work recommends a few simple steps you can take to increase your power: (1) be visible; (2) emphasize the aspects you're good at; (3) make those in power feel good about themselves; (4) if you must point out a mistake by someone in power, blame the situation or others; and shower those above with flattery.
Bottom line: worry about your relationship with your boss more than you worry about your performance.
When you get really rich and powerful, don't forget to make a donation to Farnam Street.