"The endangered cause" has a layered meaning -- while Don Jose means Ribierism, it could also, at this critical moment in Decoud's struggle between skepticism and passion, mean any cause, i.e., "now is the time for intellect and conscience to accept the validity of passion." In the next paragraph Decoud proceeds to succumb to the lure of political committment, of love, in short, of the dream-ideal as embodied and symbolized for him by Antonia.