Judges shielded from politics and political pressure because of Article III which is designed to protect judges from political pressure by granting them life tenure and prohibiting reduction of their salaries while they serve (pg. 605). The courts were also established under the provisions in Article I.
They are vulnerable to political pressure because they are appointed by the president for fixed terms of 15 years, and they are not protected by the Constitution from salary reduction (pg. 605).
Suppose the federal courts did not have the power of judicial review. Instead, all acts of Congress