"The President has a quick and able mind, though not everybody gives him that, not by a long shot"

This quote by Herman Wouk is referring to the President's intelligence and capability to think rapidly. Wouk is indicating that not everyone acknowledges the President's intelligence, and that there are many people who do not offer him credit for his mental abilities. This might be due to a variety of reasons, such as political distinctions, individual biases, or merely a lack of understanding of the President's capabilities. Wouk is stressing that the President has a fast and able mind, even if not everybody acknowledges it. This could be analyzed as a call for individuals to acknowledge the President's intelligence and to give him the credit he is worthy of. It could also be seen as a pointer that the President is capable of making decisions and leading the nation, even if not everybody agrees with his decisions.